diff --git a/java/change-notes/2021-03-05-regex-utils.md b/java/change-notes/2021-03-05-regex-utils.md
new file mode 100644
index 000000000000..666aa73f29e5
--- /dev/null
+++ b/java/change-notes/2021-03-05-regex-utils.md
@@ -0,0 +1,2 @@
+lgtm,codescanning
+* Added models for Apache Commons Lang's `RegExUtils` class. This means that any query that tracks tainted data may return additional results in cases where a `RegExUtils` transformation is part of the path from source to sink.
diff --git a/java/ql/src/semmle/code/java/frameworks/apache/Lang.qll b/java/ql/src/semmle/code/java/frameworks/apache/Lang.qll
index 26b52b2716b9..b2fb782899ca 100644
--- a/java/ql/src/semmle/code/java/frameworks/apache/Lang.qll
+++ b/java/ql/src/semmle/code/java/frameworks/apache/Lang.qll
@@ -376,3 +376,23 @@ private class ApacheStrSubstitutorModel extends SummaryModelCsv {
       ]
   }
 }
+
+/**
+ * Taint-propagating models for `RegexUtils`.
+ */
+private class ApacheRegExUtilsModel extends SummaryModelCsv {
+  override predicate row(string row) {
+    row =
+      [
+        "org.apache.commons.lang3;RegExUtils;false;removeAll;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;removeFirst;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;removePattern;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replaceAll;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replaceFirst;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replacePattern;;;Argument[0];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replaceAll;;;Argument[2];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replaceFirst;;;Argument[2];ReturnValue;taint",
+        "org.apache.commons.lang3;RegExUtils;false;replacePattern;;;Argument[2];ReturnValue;taint"
+      ]
+  }
+}
diff --git a/java/ql/test/library-tests/frameworks/apache-commons-lang3/RegExUtilsTest.java b/java/ql/test/library-tests/frameworks/apache-commons-lang3/RegExUtilsTest.java
new file mode 100644
index 000000000000..59db473d886c
--- /dev/null
+++ b/java/ql/test/library-tests/frameworks/apache-commons-lang3/RegExUtilsTest.java
@@ -0,0 +1,45 @@
+import org.apache.commons.lang3.RegExUtils;
+import java.util.regex.Pattern;
+
+public class RegExUtilsTest {
+  String taint() { return "tainted"; }
+
+  void sink(Object o) {}
+
+  void test() throws Exception {
+    Pattern cleanPattern = Pattern.compile("clean");
+    Pattern taintedPattern = Pattern.compile(taint());
+
+    sink(RegExUtils.removeAll(taint(), cleanPattern)); // $hasTaintFlow
+    sink(RegExUtils.removeAll(taint(), "clean")); // $hasTaintFlow
+    sink(RegExUtils.removeFirst(taint(), cleanPattern)); // $hasTaintFlow
+    sink(RegExUtils.removeFirst(taint(), "clean")); // $hasTaintFlow
+    sink(RegExUtils.removePattern(taint(), "clean")); // $hasTaintFlow
+    sink(RegExUtils.replaceAll(taint(), cleanPattern, "replacement")); // $hasTaintFlow
+    sink(RegExUtils.replaceAll(taint(), "clean", "replacement")); // $hasTaintFlow
+    sink(RegExUtils.replaceFirst(taint(), cleanPattern, "replacement")); // $hasTaintFlow
+    sink(RegExUtils.replaceFirst(taint(), "clean", "replacement")); // $hasTaintFlow
+    sink(RegExUtils.replacePattern(taint(), "clean", "replacement")); // $hasTaintFlow
+    sink(RegExUtils.replaceAll("original", cleanPattern, taint())); // $hasTaintFlow
+    sink(RegExUtils.replaceAll("original", "clean", taint())); // $hasTaintFlow
+    sink(RegExUtils.replaceFirst("original", cleanPattern, taint())); // $hasTaintFlow
+    sink(RegExUtils.replaceFirst("original", "clean", taint())); // $hasTaintFlow
+    sink(RegExUtils.replacePattern("original", "clean", taint())); // $hasTaintFlow
+    // Subsequent calls don't propagate taint, as regex search patterns don't propagate to the return value.
+    sink(RegExUtils.removeAll("original", taintedPattern));
+    sink(RegExUtils.removeAll("original", taint()));
+    sink(RegExUtils.removeFirst("original", taintedPattern));
+    sink(RegExUtils.removeFirst("original", taint()));
+    sink(RegExUtils.removePattern("original", taint()));
+    sink(RegExUtils.replaceAll("original", taintedPattern, "replacement"));
+    sink(RegExUtils.replaceAll("original", taint(), "replacement"));
+    sink(RegExUtils.replaceFirst("original", taintedPattern, "replacement"));
+    sink(RegExUtils.replaceFirst("original", taint(), "replacement"));
+    sink(RegExUtils.replacePattern("original", taint(), "replacement"));
+    sink(RegExUtils.replaceAll("original", taintedPattern, "replacement"));
+    sink(RegExUtils.replaceAll("original", taint(), "replacement"));
+    sink(RegExUtils.replaceFirst("original", taintedPattern, "replacement"));
+    sink(RegExUtils.replaceFirst("original", taint(), "replacement"));
+    sink(RegExUtils.replacePattern("original", taint(), "replacement"));
+  }
+}
\ No newline at end of file
diff --git a/java/ql/test/stubs/apache-commons-lang3-3.7/org/apache/commons/lang3/RegExUtils.java b/java/ql/test/stubs/apache-commons-lang3-3.7/org/apache/commons/lang3/RegExUtils.java
new file mode 100644
index 000000000000..adf128229b67
--- /dev/null
+++ b/java/ql/test/stubs/apache-commons-lang3-3.7/org/apache/commons/lang3/RegExUtils.java
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.lang3;
+
+import java.util.regex.Pattern;
+
+public class RegExUtils {
+    public static String removeAll(final String text, final Pattern regex) {
+      return null;
+    }
+
+    public static String removeAll(final String text, final String regex) {
+      return null;
+    }
+
+    public static String removeFirst(final String text, final Pattern regex) {
+      return null;
+    }
+
+    public static String removeFirst(final String text, final String regex) {
+      return null;
+    }
+
+    public static String removePattern(final String text, final String regex) {
+      return null;
+    }
+
+    public static String replaceAll(final String text, final Pattern regex, final String replacement) {
+      return null;
+    }
+
+    public static String replaceAll(final String text, final String regex, final String replacement) {
+      return null;
+    }
+
+    public static String replaceFirst(final String text, final Pattern regex, final String replacement) {
+      return null;
+    }
+
+    public static String replaceFirst(final String text, final String regex, final String replacement) {
+      return null;
+    }
+
+    public static String replacePattern(final String text, final String regex, final String replacement) {
+      return null;
+    }
+
+}