diff --git a/src/core/operations/FromCaseInsensitiveRegex.mjs b/src/core/operations/FromCaseInsensitiveRegex.mjs
new file mode 100644
index 00000000..2448c5e5
--- /dev/null
+++ b/src/core/operations/FromCaseInsensitiveRegex.mjs
@@ -0,0 +1,39 @@
+/**
+ * @author masq [github.cyberchef@masq.cc]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+
+/**
+ * From Case Insensitive Regex operation
+ */
+class FromCaseInsensitiveRegex extends Operation {
+
+    /**
+     * FromCaseInsensitiveRegex constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "From Case Insensitive Regex";
+        this.module = "Default";
+        this.description = "Converts a case-insensitive regex string to a case sensitive regex string (no guarantee on it being the proper original casing) in case /i wasn't available at the time but now is, or you need it to be case-sensitive again.";
+        this.infoURL = "https://wikipedia.org/wiki/Regular_expression";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        return input.replace(/\[[a-z]{2}\]/ig, m => m[1].toUpperCase() === m[2].toUpperCase() ? m[1] : m);
+    }
+}
+
+export default FromCaseInsensitiveRegex;