diff --git a/libc/NOTICE b/libc/NOTICE
index 9d55592..4d3a108 100644
--- a/libc/NOTICE
+++ b/libc/NOTICE
@@ -894,6 +894,34 @@
 
 -------------------------------------------------------------------
 
+Copyright (C) 2023 The Android Open Source Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in
+   the documentation and/or other materials provided with the
+   distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
+
+-------------------------------------------------------------------
+
 Copyright (c) 1980, 1983, 1988, 1993
    The Regents of the University of California.  All rights reserved.
 
diff --git a/libc/include/utmp.h b/libc/include/utmp.h
index 7aa5718..d249f8a 100644
--- a/libc/include/utmp.h
+++ b/libc/include/utmp.h
@@ -30,7 +30,7 @@
 
 /**
  * @file utmp.h
- * @brief POSIX login records.
+ * @brief No-op implementation of non-POSIX login records. See <utmpx.h> for the POSIX equivalents.
  */
 
 #include <sys/cdefs.h>
@@ -69,12 +69,12 @@
 };
 
 struct exit_status {
-  short int e_termination;
-  short int e_exit;
+  short e_termination;
+  short e_exit;
 };
 
 struct utmp {
-  short int ut_type;
+  short ut_type;
   pid_t ut_pid;
   char ut_line[UT_LINESIZE];
   char ut_id[4];
@@ -83,7 +83,7 @@
 
   struct exit_status ut_exit;
 
-  long int ut_session;
+  long ut_session;
   struct timeval ut_tv;
 
   int32_t ut_addr_v6[4];
@@ -97,21 +97,25 @@
 __BEGIN_DECLS
 
 /**
- * Does nothing.
+ * Returns -1 and sets errno to ENOTSUP.
  */
 int utmpname(const char* _Nonnull __path);
+
 /**
  * Does nothing.
  */
 void setutent(void);
+
 /**
- * Does nothing.
+ * Does nothing and returns null.
  */
 struct utmp* _Nullable getutent(void);
+
 /**
- * Does nothing.
+ * Does nothing and returns null.
  */
 struct utmp* _Nullable pututline(const struct utmp* _Nonnull __entry);
+
 /**
  * Does nothing.
  */
diff --git a/libc/include/utmpx.h b/libc/include/utmpx.h
new file mode 100644
index 0000000..5ed8e1a
--- /dev/null
+++ b/libc/include/utmpx.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+/**
+ * @file utmpx.h
+ * @brief No-op implementation of POSIX login records.
+ */
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+#include <time.h>
+
+#define EMPTY         0
+#define RUN_LVL       1
+#define BOOT_TIME     2
+#define NEW_TIME      3
+#define OLD_TIME      4
+#define INIT_PROCESS  5
+#define LOGIN_PROCESS 6
+#define USER_PROCESS  7
+#define DEAD_PROCESS  8
+#define ACCOUNTING    9
+
+struct utmpx {
+  short ut_type;
+  pid_t ut_pid;
+  char ut_line[32];
+  char ut_id[4];
+  char ut_user[32];
+  char ut_host[256];
+
+  struct {
+    short e_termination;
+    short e_exit;
+  } ut_exit;
+
+  long ut_session;
+  struct timeval ut_tv;
+
+  int32_t ut_addr_v6[4];
+  char unused[20];
+};
+
+__BEGIN_DECLS
+
+/**
+ * Does nothing.
+ */
+void setutxent(void) __RENAME(setutent);
+
+/**
+ * Does nothing and returns null.
+ */
+struct utmpx* _Nullable getutxent(void) __RENAME(getutent);
+
+/**
+ * Does nothing and returns null.
+ */
+struct utmpx* _Nullable getutxid(const struct utmpx* _Nonnull __entry) __RENAME(getutent);
+
+/**
+ * Does nothing and returns null.
+ */
+struct utmpx* _Nullable getutxline(const struct utmpx* _Nonnull __entry) __RENAME(getutent);
+
+/**
+ * Does nothing and returns null.
+ */
+struct utmpx* _Nullable pututxline(const struct utmpx* _Nonnull __entry) __RENAME(pututline);
+
+/**
+ * Does nothing.
+ */
+void endutxent(void) __RENAME(endutent);
+
+__END_DECLS
diff --git a/tests/Android.bp b/tests/Android.bp
index 6d2a8d4..1949079 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -514,6 +514,7 @@
         "unistd_test.cpp",
         "utils.cpp",
         "utmp_test.cpp",
+        "utmpx_test.cpp",
         "wchar_test.cpp",
         "wctype_test.cpp",
     ],
diff --git a/tests/NOTICE b/tests/NOTICE
index 167f90b..cc99d20 100644
--- a/tests/NOTICE
+++ b/tests/NOTICE
@@ -426,3 +426,31 @@
 
 -------------------------------------------------------------------
 
+Copyright (C) 2023 The Android Open Source Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in
+   the documentation and/or other materials provided with the
+   distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
+
+-------------------------------------------------------------------
+
diff --git a/tests/headers/posix/utmpx_h.c b/tests/headers/posix/utmpx_h.c
new file mode 100644
index 0000000..44dfac9
--- /dev/null
+++ b/tests/headers/posix/utmpx_h.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <utmpx.h>
+
+#include "header_checks.h"
+
+static void utmpx_h() {
+  TYPE(struct utmpx);
+  STRUCT_MEMBER_ARRAY(struct utmpx, char/*[]*/, ut_user);
+  STRUCT_MEMBER_ARRAY(struct utmpx, char/*[]*/, ut_id);
+  STRUCT_MEMBER_ARRAY(struct utmpx, char/*[]*/, ut_line);
+  STRUCT_MEMBER(struct utmpx, pid_t, ut_pid);
+  STRUCT_MEMBER(struct utmpx, short, ut_type);
+#if !defined(__GLIBC__)
+  // POSIX says struct timeval, but glibc has an anonymous struct.
+  STRUCT_MEMBER(struct utmpx, struct timeval, ut_tv);
+#endif
+
+  TYPE(pid_t);
+  TYPE(struct timeval);
+
+  MACRO(EMPTY);
+  MACRO(BOOT_TIME);
+  MACRO(OLD_TIME);
+  MACRO(NEW_TIME);
+  MACRO(USER_PROCESS);
+  MACRO(INIT_PROCESS);
+  MACRO(LOGIN_PROCESS);
+  MACRO(DEAD_PROCESS);
+
+  FUNCTION(endutxent, void (*f)(void));
+  FUNCTION(getutxent, struct utmpx* (*f)(void));
+  FUNCTION(getutxid, struct utmpx* (*f)(const struct utmpx*));
+  FUNCTION(getutxline, struct utmpx* (*f)(const struct utmpx*));
+  FUNCTION(pututxline, struct utmpx* (*f)(const struct utmpx*));
+  FUNCTION(setutxent, void (*f)(void));
+}
diff --git a/tests/utmp_test.cpp b/tests/utmp_test.cpp
index b024818..459f9c3 100644
--- a/tests/utmp_test.cpp
+++ b/tests/utmp_test.cpp
@@ -25,6 +25,7 @@
 }
 
 TEST(utmp, smoke) {
+  // The rest of <utmp.h> is just no-op implementations, so testing is trivial.
   ASSERT_EQ(-1, utmpname("hello"));
   setutent();
   ASSERT_EQ(NULL, getutent());
diff --git a/tests/utmpx_test.cpp b/tests/utmpx_test.cpp
new file mode 100644
index 0000000..55427a6
--- /dev/null
+++ b/tests/utmpx_test.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <gtest/gtest.h>
+
+#include <utmpx.h>
+
+TEST(utmpx, smoke) {
+  // Our utmpx "implementation" just calls the utmp no-op functions.
+  setutxent();
+  utmpx empty = {.ut_type = EMPTY};
+  ASSERT_EQ(NULL, getutxent());
+  ASSERT_EQ(NULL, getutxid(&empty));
+  ASSERT_EQ(NULL, getutxline(&empty));
+  endutxent();
+  ASSERT_EQ(NULL, pututxline(&empty));
+}