diff --git a/modules/03-number-extensions.js b/modules/03-number-extensions.js
new file mode 100644
index 0000000000000000000000000000000000000000..eca0e6e881449a1213d0a372443d5bb96d19c38e
--- /dev/null
+++ b/modules/03-number-extensions.js
@@ -0,0 +1,23 @@
+/**
+ * Returns true if the given number is between min and max, inclusive.
+ *
+ * @param {number} min Lowest value.
+ * @param {number} max Highest value.
+ * @returns {boolean} Whether given number between min and max, inclusive.
+ */
+Object.defineProperty(Number.prototype, "between", {
+	configurable: true,
+	writable: true,
+
+	value(min, max) {
+		if (min > max) {
+			Errors.report("[Number.between]: min must be less than or equal to max.", {
+				min,
+				max,
+				Stacktrace: Utils.GetStack(),
+			});
+			return false;
+		}
+		return this >= min && this <= max;
+	},
+});