diff --git a/CHANGELOG.md b/CHANGELOG.md
index d9b8eff0..4761b540 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 All major and minor version changes will be documented in this file. Details of patch-level version changes can be found in [commit messages](https://github.com/gchq/CyberChef/commits/master).
 
 
+### [8.21.0] - 2019-01-10
+- 'To Case Insensitive Regex' and 'From Case Insensitive Regex' operations added [@masq] | [#461]
+
 ### [8.20.0] - 2019-01-09
 - 'Generate Lorem Ipsum' operation added [@klaxon1] | [#455]
 
@@ -91,6 +94,7 @@ All major and minor version changes will be documented in this file. Details of
 
 
 
+[8.21.0]: https://github.com/gchq/CyberChef/releases/tag/v8.21.0
 [8.20.0]: https://github.com/gchq/CyberChef/releases/tag/v8.20.0
 [8.19.0]: https://github.com/gchq/CyberChef/releases/tag/v8.19.0
 [8.18.0]: https://github.com/gchq/CyberChef/releases/tag/v8.18.0
@@ -134,6 +138,7 @@ All major and minor version changes will be documented in this file. Details of
 [@tcode2k16]: https://github.com/tcode2k16
 [@Cynser]: https://github.com/Cynser
 [@anthony-arnold]: https://github.com/anthony-arnold
+[@masq]: https://github.com/masq
 
 [#95]: https://github.com/gchq/CyberChef/pull/299
 [#173]: https://github.com/gchq/CyberChef/pull/173
@@ -165,3 +170,4 @@ All major and minor version changes will be documented in this file. Details of
 [#449]: https://github.com/gchq/CyberChef/pull/449
 [#455]: https://github.com/gchq/CyberChef/pull/455
 [#458]: https://github.com/gchq/CyberChef/pull/458
+[#461]: https://github.com/gchq/CyberChef/pull/461
diff --git a/src/core/config/Categories.json b/src/core/config/Categories.json
index 3e792b99..9d56acf2 100755
--- a/src/core/config/Categories.json
+++ b/src/core/config/Categories.json
@@ -189,6 +189,8 @@
             "Remove null bytes",
             "To Upper case",
             "To Lower case",
+			"To Case Insensitive Regex",
+			"From Case Insensitive Regex",
             "Add line numbers",
             "Remove line numbers",
             "To Table",
diff --git a/src/core/operations/FromCaseInsensitiveRegex.mjs b/src/core/operations/FromCaseInsensitiveRegex.mjs
new file mode 100644
index 00000000..36cd9b14
--- /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 the i flag wasn't available at the time but now is, or you need it to be case-sensitive again.<br><br>e.g. <code>[mM][oO][zZ][iI][lL][lL][aA]/[0-9].[0-9] .*</code> becomes <code>Mozilla/[0-9].[0-9] .*</code>";
+        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;
diff --git a/src/core/operations/ToCaseInsensitiveRegex.mjs b/src/core/operations/ToCaseInsensitiveRegex.mjs
new file mode 100644
index 00000000..0d606a05
--- /dev/null
+++ b/src/core/operations/ToCaseInsensitiveRegex.mjs
@@ -0,0 +1,39 @@
+/**
+ * @author masq [github.cyberchef@masq.cc]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+
+/**
+ * To Case Insensitive Regex operation
+ */
+class ToCaseInsensitiveRegex extends Operation {
+
+    /**
+     * ToCaseInsensitiveRegex constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "To Case Insensitive Regex";
+        this.module = "Default";
+        this.description = "Converts a case-sensitive regex string into a case-insensitive regex string in case the i flag is unavailable to you.<br><br>e.g. <code>Mozilla/[0-9].[0-9] .*</code> becomes <code>[mM][oO][zZ][iI][lL][lL][aA]/[0-9].[0-9] .*</code>";
+        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]/ig, m => `[${m.toLowerCase()}${m.toUpperCase()}]`);
+    }
+}
+
+export default ToCaseInsensitiveRegex;
diff --git a/tests/operations/index.mjs b/tests/operations/index.mjs
index da9d41be..22a9276d 100644
--- a/tests/operations/index.mjs
+++ b/tests/operations/index.mjs
@@ -82,6 +82,7 @@ import "./tests/TranslateDateTimeFormat";
 import "./tests/Magic";
 import "./tests/ParseTLV";
 import "./tests/Media";
+import "./tests/ToFromInsensitiveRegex";
 
 // Cannot test operations that use the File type yet
 //import "./tests/SplitColourChannels";
diff --git a/tests/operations/tests/ToFromInsensitiveRegex.mjs b/tests/operations/tests/ToFromInsensitiveRegex.mjs
new file mode 100644
index 00000000..fa191951
--- /dev/null
+++ b/tests/operations/tests/ToFromInsensitiveRegex.mjs
@@ -0,0 +1,56 @@
+/**
+ * To/From Case Insensitive Regex tests.
+ *
+ * @author masq [github.cyberchef@masq.cc]
+ *
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+import TestRegister from "../TestRegister";
+
+TestRegister.addTests([
+    {
+        name: "To Case Insensitive Regex: nothing",
+        input: "",
+        expectedOutput: "",
+        recipeConfig: [
+            {
+                op: "To Case Insensitive Regex",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "From Case Insensitive Regex: nothing",
+        input: "",
+        expectedOutput: "",
+        recipeConfig: [
+            {
+                op: "From Case Insensitive Regex",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "To Case Insensitive Regex: simple test",
+        input: "S0meth!ng",
+        expectedOutput: "[sS]0[mM][eE][tT][hH]![nN][gG]",
+        recipeConfig: [
+            {
+                op: "To Case Insensitive Regex",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "From Case Insensitive Regex: simple test",
+        input: "[sS]0[mM][eE][tT][hH]![nN][Gg] [wr][On][g]?",
+        expectedOutput: "s0meth!nG [wr][On][g]?",
+        recipeConfig: [
+            {
+                op: "From Case Insensitive Regex",
+                args: [],
+            },
+        ],
+    },
+]);