diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74e52b7..3e227e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,8 @@
 - X10D.Unity: Added `GameObject.SetLayerRecursively(int)`
 - X10D.Unity: Added `GameObject.SetParent(GameObject[, bool])`
 - X10D.Unity: Added `GameObject.SetParent(Transform[, bool])`
+- X10D.Unity: Added `System.Numerics.Quaternion.ToUnityQuaternion()`
+- X10D.Unity: Added `Quaternion.ToSystemQuaternion()`
 - X10D.Unity: Added `Random.NextColorArgb()`
 - X10D.Unity: Added `Random.NextColor32Argb()`
 - X10D.Unity: Added `Random.NextColorRgb()`
@@ -54,6 +56,12 @@
 - X10D.Unity: Added `Random.NextUnitVector3()`
 - X10D.Unity: Added `Transform.LookAt(GameObject[, Vector3])`
 - X10D.Unity: Added `Transform.SetParent(GameObject[, bool])`
+- X10D.Unity: Added `System.Numerics.Vector2.ToUnityVector()`
+- X10D.Unity: Added `System.Numerics.Vector3.ToUnityVector()`
+- X10D.Unity: Added `System.Numerics.Vector4.ToUnityVector()`
+- X10D.Unity: Added `Vector2.ToSystemVector()`
+- X10D.Unity: Added `Vector3.ToSystemVector()`
+- X10D.Unity: Added `Vector4.ToSystemVector()`
 - X10D.Unity: Added `Vector2.WithX()`
 - X10D.Unity: Added `Vector2.WithY()`
 - X10D.Unity: Added `Vector3.WithX()`
diff --git a/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs b/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs
new file mode 100644
index 0000000..a486a75
--- /dev/null
+++ b/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs
@@ -0,0 +1,53 @@
+using System.Collections;
+using NUnit.Framework;
+using UnityEngine;
+using UnityEngine.TestTools;
+using X10D.Core;
+using X10D.Unity.Numerics;
+using Random = System.Random;
+
+namespace X10D.Unity.Tests.Numerics
+{
+    public class QuaternionTests
+    {
+        [UnityTest]
+        public IEnumerator ToSystemQuaternion_ShouldReturnQuaternion_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+            float w = random.NextSingle();
+
+            var quaternion = new Quaternion(x, y, z, w);
+            var systemQuaternion = quaternion.ToSystemQuaternion();
+
+            Assert.AreEqual(quaternion.x, systemQuaternion.X, 1e-6f);
+            Assert.AreEqual(quaternion.y, systemQuaternion.Y, 1e-6f);
+            Assert.AreEqual(quaternion.z, systemQuaternion.Z, 1e-6f);
+            Assert.AreEqual(quaternion.w, systemQuaternion.W, 1e-6f);
+
+            yield break;
+        }
+
+        [UnityTest]
+        public IEnumerator ToUnityQuaternion_ShouldReturnQuaternion_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+            float w = random.NextSingle();
+
+            var quaternion = new System.Numerics.Quaternion(x, y, z, w);
+            var unityQuaternion = quaternion.ToUnityQuaternion();
+
+            Assert.AreEqual(quaternion.X, unityQuaternion.x, 1e-6f);
+            Assert.AreEqual(quaternion.Y, unityQuaternion.y, 1e-6f);
+            Assert.AreEqual(quaternion.Z, unityQuaternion.z, 1e-6f);
+            Assert.AreEqual(quaternion.W, unityQuaternion.w, 1e-6f);
+
+            yield break;
+        }
+    }
+}
diff --git a/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs.meta b/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs.meta
new file mode 100644
index 0000000..a8117be
--- /dev/null
+++ b/X10D.Unity.Tests/Assets/Tests/Numerics/QuaternionTests.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: a395fec41c5a4e9d9ffb05324e8159b0
+timeCreated: 1652124913
\ No newline at end of file
diff --git a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector2Tests.cs b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector2Tests.cs
index 45c2526..3fc09e2 100644
--- a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector2Tests.cs
+++ b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector2Tests.cs
@@ -2,12 +2,48 @@
 using NUnit.Framework;
 using UnityEngine;
 using UnityEngine.TestTools;
+using X10D.Core;
 using X10D.Unity.Numerics;
+using Random = System.Random;
 
 namespace X10D.Unity.Tests.Numerics
 {
     public class Vector2Tests
     {
+        [UnityTest]
+        public IEnumerator ToSystemVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+
+            var vector = new Vector2(x, y);
+            var systemVector = vector.ToSystemVector();
+
+            Assert.AreEqual(vector.magnitude, systemVector.Length(), 1e-6f);
+            Assert.AreEqual(vector.x, systemVector.X, 1e-6f);
+            Assert.AreEqual(vector.y, systemVector.Y, 1e-6f);
+
+            yield break;
+        }
+
+        [UnityTest]
+        public IEnumerator ToUnityVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+
+            var vector = new System.Numerics.Vector2(x, y);
+            var unityVector = vector.ToUnityVector();
+
+            Assert.AreEqual(vector.Length(), unityVector.magnitude, 1e-6f);
+            Assert.AreEqual(vector.X, unityVector.x, 1e-6f);
+            Assert.AreEqual(vector.Y, unityVector.y, 1e-6f);
+
+            yield break;
+        }
+
         [UnityTest]
         public IEnumerator WithX_ShouldReturnVectorWithNewX_GivenVector()
         {
diff --git a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector3Tests.cs b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector3Tests.cs
index cf7ad8c..f14c7e3 100644
--- a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector3Tests.cs
+++ b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector3Tests.cs
@@ -2,12 +2,52 @@
 using NUnit.Framework;
 using UnityEngine;
 using UnityEngine.TestTools;
+using X10D.Core;
 using X10D.Unity.Numerics;
+using Random = System.Random;
 
 namespace X10D.Unity.Tests.Numerics
 {
     public class Vector3Tests
     {
+        [UnityTest]
+        public IEnumerator ToSystemVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+
+            var vector = new Vector3(x, y, z);
+            var systemVector = vector.ToSystemVector();
+
+            Assert.AreEqual(vector.magnitude, systemVector.Length(), 1e-6f);
+            Assert.AreEqual(vector.x, systemVector.X, 1e-6f);
+            Assert.AreEqual(vector.y, systemVector.Y, 1e-6f);
+            Assert.AreEqual(vector.z, systemVector.Z, 1e-6f);
+
+            yield break;
+        }
+
+        [UnityTest]
+        public IEnumerator ToUnityVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+
+            var vector = new System.Numerics.Vector3(x, y, z);
+            var unityVector = vector.ToUnityVector();
+
+            Assert.AreEqual(vector.Length(), unityVector.magnitude, 1e-6f);
+            Assert.AreEqual(vector.X, unityVector.x, 1e-6f);
+            Assert.AreEqual(vector.Y, unityVector.y, 1e-6f);
+            Assert.AreEqual(vector.Z, unityVector.z, 1e-6f);
+
+            yield break;
+        }
+
         [UnityTest]
         public IEnumerator WithX_ShouldReturnVectorWithNewX_GivenVector()
         {
diff --git a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector4Tests.cs b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector4Tests.cs
index 2e79b3f..d400512 100644
--- a/X10D.Unity.Tests/Assets/Tests/Numerics/Vector4Tests.cs
+++ b/X10D.Unity.Tests/Assets/Tests/Numerics/Vector4Tests.cs
@@ -2,12 +2,56 @@
 using NUnit.Framework;
 using UnityEngine;
 using UnityEngine.TestTools;
+using X10D.Core;
 using X10D.Unity.Numerics;
+using Random = System.Random;
 
 namespace X10D.Unity.Tests.Numerics
 {
     public class Vector4Tests
     {
+        [UnityTest]
+        public IEnumerator ToSystemVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+            float w = random.NextSingle();
+
+            var vector = new Vector4(x, y, z, w);
+            var systemVector = vector.ToSystemVector();
+
+            Assert.AreEqual(vector.magnitude, systemVector.Length(), 1e-6f);
+            Assert.AreEqual(vector.x, systemVector.X, 1e-6f);
+            Assert.AreEqual(vector.y, systemVector.Y, 1e-6f);
+            Assert.AreEqual(vector.z, systemVector.Z, 1e-6f);
+            Assert.AreEqual(vector.w, systemVector.W, 1e-6f);
+
+            yield break;
+        }
+
+        [UnityTest]
+        public IEnumerator ToUnityVector_ShouldReturnVector_WithEqualComponents()
+        {
+            var random = new Random();
+            float x = random.NextSingle();
+            float y = random.NextSingle();
+            float z = random.NextSingle();
+            float w = random.NextSingle();
+
+            var vector = new System.Numerics.Vector4(x, y, z, w);
+            var unityVector = vector.ToUnityVector();
+
+            Assert.AreEqual(vector.Length(), unityVector.magnitude, 1e-6f);
+            Assert.AreEqual(vector.X, unityVector.x, 1e-6f);
+            Assert.AreEqual(vector.Y, unityVector.y, 1e-6f);
+            Assert.AreEqual(vector.Z, unityVector.z, 1e-6f);
+            Assert.AreEqual(vector.W, unityVector.w, 1e-6f);
+
+            yield break;
+        }
+
         [UnityTest]
         public IEnumerator WithW_ShouldReturnVectorWithNewW_GivenVector()
         {
@@ -24,7 +68,7 @@ namespace X10D.Unity.Tests.Numerics
             Assert.AreEqual(new Vector4(1, 0, 0, 1), new Vector4(1, 0, 0, 0).WithW(1));
             Assert.AreEqual(new Vector4(0, 1, 0, 1), new Vector4(0, 1, 0, 0).WithW(1));
             Assert.AreEqual(new Vector4(0, 0, 1, 1), new Vector4(0, 0, 1, 0).WithW(1));
-            
+
             yield break;
         }
 
@@ -44,7 +88,7 @@ namespace X10D.Unity.Tests.Numerics
             Assert.AreEqual(new Vector4(1, 0, 0, 0), new Vector4(1, 0, 0, 0).WithX(1));
             Assert.AreEqual(new Vector4(1, 1, 0, 0), new Vector4(0, 1, 0, 0).WithX(1));
             Assert.AreEqual(new Vector4(1, 0, 1, 0), new Vector4(0, 0, 1, 0).WithX(1));
-            
+
             yield break;
         }
 
@@ -64,7 +108,7 @@ namespace X10D.Unity.Tests.Numerics
             Assert.AreEqual(new Vector4(1, 1, 0, 0), new Vector4(1, 0, 0, 0).WithY(1));
             Assert.AreEqual(new Vector4(0, 1, 0, 0), new Vector4(0, 1, 0, 0).WithY(1));
             Assert.AreEqual(new Vector4(0, 1, 1, 0), new Vector4(0, 0, 1, 0).WithY(1));
-            
+
             yield break;
         }
 
@@ -84,7 +128,7 @@ namespace X10D.Unity.Tests.Numerics
             Assert.AreEqual(new Vector4(1, 0, 1, 0), new Vector4(1, 0, 0, 0).WithZ(1));
             Assert.AreEqual(new Vector4(0, 1, 1, 0), new Vector4(0, 1, 0, 0).WithZ(1));
             Assert.AreEqual(new Vector4(0, 0, 1, 0), new Vector4(0, 0, 1, 0).WithZ(1));
-            
+
             yield break;
         }
     }
diff --git a/X10D.Unity/src/Numerics/QuaternionExtensions.cs b/X10D.Unity/src/Numerics/QuaternionExtensions.cs
new file mode 100644
index 0000000..2c6355e
--- /dev/null
+++ b/X10D.Unity/src/Numerics/QuaternionExtensions.cs
@@ -0,0 +1,35 @@
+using System.Diagnostics.Contracts;
+using System.Runtime.CompilerServices;
+using UnityEngine;
+
+namespace X10D.Unity.Numerics;
+
+/// <summary>
+///     Numeric-extensions for <see cref="Quaternion" />.
+/// </summary>
+public static class QuaternionExtensions
+{
+    /// <summary>
+    ///     Converts the current quaternion to a <see cref="System.Numerics.Quaternion" />.
+    /// </summary>
+    /// <param name="quaternion">The quaternion to convert.</param>
+    /// <returns>The converted quaternion.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static System.Numerics.Quaternion ToSystemQuaternion(this Quaternion quaternion)
+    {
+        return new System.Numerics.Quaternion(quaternion.x, quaternion.y, quaternion.z, quaternion.w);
+    }
+
+    /// <summary>
+    ///     Converts the current quaternion to a <see cref="Quaternion" />.
+    /// </summary>
+    /// <param name="quaternion">The quaternion to convert.</param>
+    /// <returns>The converted quaternion.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Quaternion ToUnityQuaternion(this System.Numerics.Quaternion quaternion)
+    {
+        return new Quaternion(quaternion.X, quaternion.Y, quaternion.Z, quaternion.W);
+    }
+}
diff --git a/X10D.Unity/src/Numerics/Vector2Extensions.cs b/X10D.Unity/src/Numerics/Vector2Extensions.cs
index 1f7b466..32ff372 100644
--- a/X10D.Unity/src/Numerics/Vector2Extensions.cs
+++ b/X10D.Unity/src/Numerics/Vector2Extensions.cs
@@ -9,6 +9,30 @@ namespace X10D.Unity.Numerics;
 /// </summary>
 public static class Vector2Extensions
 {
+    /// <summary>
+    ///     Converts the current vector to a <see cref="System.Numerics.Vector2" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static System.Numerics.Vector2 ToSystemVector(this Vector2 vector)
+    {
+        return new System.Numerics.Vector2(vector.x, vector.y);
+    }
+
+    /// <summary>
+    ///     Converts the current vector to a <see cref="Vector2" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector2 ToUnityVector(this System.Numerics.Vector2 vector)
+    {
+        return new Vector2(vector.X, vector.Y);
+    }
+
     /// <summary>
     ///     Returns a vector whose Y component is the same as the specified vector, and whose X component is a new value.
     /// </summary>
diff --git a/X10D.Unity/src/Numerics/Vector3Extensions.cs b/X10D.Unity/src/Numerics/Vector3Extensions.cs
index 52e0f56..1b725ce 100644
--- a/X10D.Unity/src/Numerics/Vector3Extensions.cs
+++ b/X10D.Unity/src/Numerics/Vector3Extensions.cs
@@ -9,6 +9,30 @@ namespace X10D.Unity.Numerics;
 /// </summary>
 public static class Vector3Extensions
 {
+    /// <summary>
+    ///     Converts the current vector to a <see cref="System.Numerics.Vector3" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static System.Numerics.Vector3 ToSystemVector(this Vector3 vector)
+    {
+        return new System.Numerics.Vector3(vector.x, vector.y, vector.z);
+    }
+
+    /// <summary>
+    ///     Converts the current vector to a <see cref="Vector3" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector3 ToUnityVector(this System.Numerics.Vector3 vector)
+    {
+        return new Vector3(vector.X, vector.Y, vector.Z);
+    }
+
     /// <summary>
     ///     Returns a vector whose Y and Z components are the same as the specified vector, and whose X component is a new value.
     /// </summary>
diff --git a/X10D.Unity/src/Numerics/Vector4Extensions.cs b/X10D.Unity/src/Numerics/Vector4Extensions.cs
index 0a21bca..ca2587f 100644
--- a/X10D.Unity/src/Numerics/Vector4Extensions.cs
+++ b/X10D.Unity/src/Numerics/Vector4Extensions.cs
@@ -9,6 +9,30 @@ namespace X10D.Unity.Numerics;
 /// </summary>
 public static class Vector4Extensions
 {
+    /// <summary>
+    ///     Converts the current vector to a <see cref="System.Numerics.Vector4" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static System.Numerics.Vector4 ToSystemVector(this Vector4 vector)
+    {
+        return new System.Numerics.Vector4(vector.x, vector.y, vector.z, vector.w);
+    }
+
+    /// <summary>
+    ///     Converts the current vector to a <see cref="Vector4" />.
+    /// </summary>
+    /// <param name="vector">The vector to convert.</param>
+    /// <returns>The converted vector.</returns>
+    [Pure]
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector4 ToUnityVector(this System.Numerics.Vector4 vector)
+    {
+        return new Vector4(vector.X, vector.Y, vector.Z, vector.W);
+    }
+
     /// <summary>
     ///     Returns a vector whose Y, Z, and W components are the same as the specified vector, and whose X component is a new
     ///     value.