diff --git a/lib/operators/index.js b/lib/operators/index.js
index c2ad910..cca52d3 100644
--- a/lib/operators/index.js
+++ b/lib/operators/index.js
@@ -5,6 +5,7 @@ module.exports = {
   IsUndefined: require('./is-undefined'),
   IsNull: require('./is-null'),
   IsPresent: require('./is-present'),
+  IsString: require('./is-string'),
   NumericEquals: require('./numeric-equals'),
   NumericGreaterThan: require('./numeric-greater-than'),
   NumericGreaterThanEquals: require('./numeric-greater-than-equals'),
diff --git a/lib/operators/is-string.js b/lib/operators/is-string.js
new file mode 100644
index 0000000..32a8e70
--- /dev/null
+++ b/lib/operators/is-string.js
@@ -0,0 +1,13 @@
+'use strict'
+
+module.exports = function isStringOperator (inputValue, comparisonValue, candidateStateName, cache) {
+  const isString = typeof inputValue === 'string'
+
+  if (isString && comparisonValue === true) {
+    return candidateStateName
+  }
+
+  if (!isString && comparisonValue !== true) {
+    return candidateStateName
+  }
+}
diff --git a/test/data-test-expr-tests.js b/test/data-test-expr-tests.js
index e5cac25..ecf266f 100644
--- a/test/data-test-expr-tests.js
+++ b/test/data-test-expr-tests.js
@@ -98,6 +98,19 @@ const tests = {
     ['nope', true, 'DefaultState'],
     [true, false, 'DefaultState'],
     [false, false, 'DefaultState']
+  ],
+  IsString: [
+    ['yep', true, 'NextState'],
+    [0, false, 'NextState'],
+    [true, false, 'NextState'],
+    [undefined, false, 'NextState'],
+    [null, false, 'NextState'],
+
+    ['yep', false, 'DefaultState'],
+    [0, true, 'DefaultState'],
+    [true, true, 'DefaultState'],
+    [undefined, true, 'DefaultState'],
+    [null, true, 'DefaultState']
   ]
 }