diff --git a/src/core/config/Categories.json b/src/core/config/Categories.json
index 307270d26..80834d4db 100644
--- a/src/core/config/Categories.json
+++ b/src/core/config/Categories.json
@@ -245,6 +245,7 @@
             "Remove null bytes",
             "To Upper case",
             "To Lower case",
+            "Swap case",
             "To Case Insensitive Regex",
             "From Case Insensitive Regex",
             "Add line numbers",
diff --git a/src/core/operations/SwapCase.mjs b/src/core/operations/SwapCase.mjs
new file mode 100644
index 000000000..e1fad7309
--- /dev/null
+++ b/src/core/operations/SwapCase.mjs
@@ -0,0 +1,77 @@
+/**
+ * @author mikecat
+ * @copyright Crown Copyright 2023
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+
+/**
+ * Swap case operation
+ */
+class SwapCase extends Operation {
+
+    /**
+     * SwapCase constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Swap case";
+        this.module = "Default";
+        this.description = "Converts uppercase letters to lowercase ones, and lowercase ones to uppercase ones.";
+        this.infoURL = "";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        let result = "";
+        for (let i = 0; i < input.length; i++) {
+            const c = input.charAt(i);
+            const upper = c.toUpperCase();
+            if (c === upper) {
+                result += c.toLowerCase();
+            } else {
+                result += upper;
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Highlight Swap case
+     *
+     * @param {Object[]} pos
+     * @param {number} pos[].start
+     * @param {number} pos[].end
+     * @param {Object[]} args
+     * @returns {Object[]} pos
+     */
+    highlight(pos, args) {
+        return pos;
+    }
+
+    /**
+     * Highlight Swap case in reverse
+     *
+     * @param {Object[]} pos
+     * @param {number} pos[].start
+     * @param {number} pos[].end
+     * @param {Object[]} args
+     * @returns {Object[]} pos
+     */
+    highlightReverse(pos, args) {
+        return pos;
+    }
+
+}
+
+export default SwapCase;
diff --git a/tests/operations/index.mjs b/tests/operations/index.mjs
index 7a3361f24..43c6a5dde 100644
--- a/tests/operations/index.mjs
+++ b/tests/operations/index.mjs
@@ -130,6 +130,7 @@ import "./tests/FletcherChecksum.mjs";
 import "./tests/CMAC.mjs";
 import "./tests/AESKeyWrap.mjs";
 import "./tests/Rabbit.mjs";
+import "./tests/SwapCase.mjs";
 
 // Cannot test operations that use the File type yet
 // import "./tests/SplitColourChannels.mjs";
diff --git a/tests/operations/tests/SwapCase.mjs b/tests/operations/tests/SwapCase.mjs
new file mode 100644
index 000000000..2506fc44b
--- /dev/null
+++ b/tests/operations/tests/SwapCase.mjs
@@ -0,0 +1,33 @@
+/**
+ * @author mikecat
+ * @copyright Crown Copyright 2023
+ * @license Apache-2.0
+ */
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        "name": "Swap Case: basic example",
+        "input": "Hello, World!",
+        "expectedOutput": "hELLO, wORLD!",
+        "recipeConfig": [
+            {
+                "op": "Swap case",
+                "args": [
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Swap Case: empty input",
+        "input": "",
+        "expectedOutput": "",
+        "recipeConfig": [
+            {
+                "op": "Swap case",
+                "args": [
+                ],
+            },
+        ],
+    },
+]);