diff --git a/src/core/config/Categories.json b/src/core/config/Categories.json
index aac00ca1..4b58d340 100644
--- a/src/core/config/Categories.json
+++ b/src/core/config/Categories.json
@@ -41,6 +41,7 @@
             "From Base",
             "To BCD",
             "From BCD",
+            "Text-Integer Conversion",
             "To HTML Entity",
             "From HTML Entity",
             "URL Encode",
diff --git a/src/core/operations/TextIntegerConverter.mjs b/src/core/operations/TextIntegerConverter.mjs
new file mode 100644
index 00000000..e7ff4547
--- /dev/null
+++ b/src/core/operations/TextIntegerConverter.mjs
@@ -0,0 +1,114 @@
+/**
+ * @author p-leriche [philip.leriche@cantab.net]
+ * @copyright Crown Copyright 2025
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+
+/* ---------- helper functions ---------- */
+
+/**
+ * Convert text to BigInt (big-endian byte interpretation)
+ */
+function textToBigInt(text) {
+    if (text.length === 0) return 0n;
+
+    let result = 0n;
+    for (let i = 0; i < text.length; i++) {
+        const charCode = BigInt(text.charCodeAt(i));
+        result = (result << 8n) | charCode;
+    }
+    return result;
+}
+
+/**
+ * Convert BigInt to text (big-endian byte interpretation)
+ */
+function bigIntToText(value) {
+    if (value === 0n) return "";
+
+    const bytes = [];
+    let num = value;
+
+    while (num > 0n) {
+        bytes.unshift(Number(num & 0xFFn));
+        num >>= 8n;
+    }
+
+    return String.fromCharCode(...bytes);
+}
+
+/* ---------- operation class ---------- */
+
+/**
+ * Text/Integer Converter operation
+ */
+class TextIntegerConverter extends Operation {
+    /**
+     * TextIntegerConverter constructor
+     */
+    constructor() {
+        super();
+
+        this.description =
+            "Converts between text strings and large integers (decimal or hexadecimal).<br><br>" +
+            "Text is interpreted as a big-endian sequence of character codes. For example:<br>" +
+            "ABC is 0x414243 (hex) is 4276803 (decimal)<br>" +
+            "<b>Input format detection:</b><br>" +
+            "Decimal: digits 0-9 only<br>" +
+            "Hexadecimal: 0x... prefix<br>" +
+            "Quoted or unquoted text: treated as string<br><br>" ;
+        this.infoURL = "https://wikipedia.org/wiki/Endianness";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [
+            {
+                name: "Output format",
+                type: "option",
+                value: ["String", "Decimal", "Hexadecimal"]
+            }
+        ];
+        this.name = "Text-Integer Conversion";
+        this.module = "Default";
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const outputFormat = args[0];
+        const trimmed = input.trim();
+
+        let bigIntValue;
+
+        if (!trimmed) {
+            // Null input - treat as zero
+            bigIntValue = 0;
+        } else if (/^0x[0-9a-f]+$/i.test(trimmed) ||
+            /^[+-]?[0-9]+$/.test(trimmed)) {
+            // Hex or decimal integer
+            bigIntValue = BigInt(trimmed);
+        } else if (/^["'].*["']$/.test(trimmed)) {
+            // Quoted string: Remove quotes and convert text to BigInt
+            const text = trimmed.slice(1, -1);
+            bigIntValue = textToBigInt(text);
+        } else {
+            // Assume it's unquoted text
+            bigIntValue = textToBigInt(trimmed);
+        }
+
+        // Convert to output format
+        if (outputFormat === "String") {
+            return bigIntToText(bigIntValue);
+        } else if (outputFormat === "Decimal") {
+            return bigIntValue.toString();
+        } else { // Hexadecimal
+            return "0x" + bigIntValue.toString(16);
+        }
+    }
+}
+
+export default TextIntegerConverter;