diff --git a/examples/evlocks.janet b/examples/evlocks.janet
new file mode 100644
index 00000000..08b497f7
--- /dev/null
+++ b/examples/evlocks.janet
@@ -0,0 +1,45 @@
+(defn sleep
+  "Sleep the entire thread, not just a single fiber."
+  [n]
+  (os/sleep (* 0.1 n)))
+
+(defn work [lock n]
+  (ev/acquire-lock lock)
+  (print "working " n "...")
+  (sleep n)
+  (print "done working...")
+  (ev/release-lock lock))
+
+(defn reader
+  [rwlock n]
+  (ev/acquire-rlock rwlock)
+  (print "reading " n "...")
+  (sleep n)
+  (print "done reading " n "...")
+  (ev/release-rlock rwlock))
+
+(defn writer
+  [rwlock n]
+  (ev/acquire-wlock rwlock)
+  (print "writing " n "...")
+  (sleep n)
+  (print "done writing...")
+  (ev/release-wlock rwlock))
+
+(defn test-lock
+  []
+  (def lock (ev/lock))
+  (for i 3 7
+    (ev/spawn-thread
+      (work lock i))))
+
+(defn test-rwlock
+  []
+  (def rwlock (ev/rwlock))
+  (for i 0 20
+    (if (> 0.1 (math/random))
+      (ev/spawn-thread (writer rwlock i))
+      (ev/spawn-thread (reader rwlock i)))))
+
+(test-rwlock)
+(test-lock)
diff --git a/src/core/abstract.c b/src/core/abstract.c
index da48ca1d..ba2e0cf5 100644
--- a/src/core/abstract.c
+++ b/src/core/abstract.c
@@ -110,6 +110,31 @@ void janet_os_mutex_unlock(JanetOSMutex *mutex) {
     LeaveCriticalSection((CRITICAL_SECTION *) mutex);
 }
 
+void janet_os_rwlock_init(JanetOSRWLock *rwlock) {
+    InitializeSRWLock((PSRWLOCK) rwlock);
+}
+
+void janet_os_rwlock_deinit(JanetOSRWLock *rwlock) {
+    /* no op? */
+    (void) rwlock;
+}
+
+void janet_os_rwlock_rlock(JanetOSRWLock *rwlock) {
+    AcquireSRWLockShared((PSRWLOCK) rwlock);
+}
+
+void janet_os_rwlock_wlock(JanetOSRWLock *rwlock) {
+    AcquireSRWLockExclusive((PSRWLOCK) rwlock);
+}
+
+void janet_os_rwlock_runlock(JanetOSRWLock *rwlock) {
+    ReleaseSRWLockShared((PSRWLOCK) rwlock);
+}
+
+void janet_os_rwlock_wunlock(JanetOSRWLock *rwlock) {
+    ReleaseSRWLockExclusive((PSRWLOCK) rwlock);
+}
+
 #else
 
 static int32_t janet_incref(JanetAbstractHead *ab) {
@@ -140,6 +165,30 @@ void janet_os_mutex_unlock(JanetOSMutex *mutex) {
     if (ret) janet_panic("cannot release lock");
 }
 
+void janet_os_rwlock_init(JanetOSRWLock *rwlock) {
+    pthread_rwlock_init(rwlock, NULL);
+}
+
+void janet_os_rwlock_deinit(JanetOSRWLock *rwlock) {
+    pthread_rwlock_destroy(rwlock);
+}
+
+void janet_os_rwlock_rlock(JanetOSRWLock *rwlock) {
+    pthread_rwlock_rdlock(rwlock);
+}
+
+void janet_os_rwlock_wlock(JanetOSRWLock *rwlock) {
+    pthread_rwlock_wrlock(rwlock);
+}
+
+void janet_os_rwlock_runlock(JanetOSRWLock *rwlock) {
+    pthread_rwlock_unlock(rwlock);
+}
+
+void janet_os_rwlock_wunlock(JanetOSRWLock *rwlock) {
+    pthread_rwlock_unlock(rwlock);
+}
+
 #endif
 
 int32_t janet_abstract_incref(void *abst) {
diff --git a/src/core/ev.c b/src/core/ev.c
index 665e651f..41931138 100644
--- a/src/core/ev.c
+++ b/src/core/ev.c
@@ -3015,7 +3015,6 @@ JANET_CORE_FN(janet_cfun_stream_write,
 
 typedef struct {
     JanetOSMutex mutex;
-    int destroyed;
 } JanetAbstractMutex;
 
 static int mutexgc(void *p, size_t size) {
@@ -3061,6 +3060,69 @@ JANET_CORE_FN(janet_cfun_mutex_release,
     return argv[0];
 }
 
+typedef struct {
+    JanetOSRWLock rwlock;
+} JanetAbstractRWLock;
+
+static int rwlockgc(void *p, size_t size) {
+    JanetAbstractRWLock *rwlock = (JanetAbstractRWLock *) p;
+    (void) size;
+    janet_os_rwlock_deinit(&rwlock->rwlock);
+    return 0;
+}
+
+const JanetAbstractType janet_rwlock_type = {
+    "core/rwlock",
+    rwlockgc,
+    JANET_ATEND_GC
+};
+
+JANET_CORE_FN(janet_cfun_rwlock,
+        "(ev/rwlock)",
+        "Create a new read-write lock to coordinate threads.") {
+    janet_fixarity(argc, 0);
+    (void) argv;
+    JanetAbstractRWLock *rwlock = janet_abstract_threaded(&janet_rwlock_type, sizeof(JanetAbstractRWLock));
+    janet_os_rwlock_init(&rwlock->rwlock);
+    return janet_wrap_abstract(rwlock);
+}
+
+JANET_CORE_FN(janet_cfun_rwlock_read_lock,
+        "(ev/acquire-rlock rwlock)",
+        "Acquire a read lock an a read-write lock.") {
+    janet_fixarity(argc, 1);
+    JanetAbstractRWLock *rwlock = janet_getabstract(argv, 0, &janet_rwlock_type);
+    janet_os_rwlock_rlock(&rwlock->rwlock);
+    return argv[0];
+}
+
+JANET_CORE_FN(janet_cfun_rwlock_write_lock,
+        "(ev/acquire-wlock rwlock)",
+        "Acquire a write lock on a read-write lock.") {
+    janet_fixarity(argc, 1);
+    JanetAbstractRWLock *rwlock = janet_getabstract(argv, 0, &janet_rwlock_type);
+    janet_os_rwlock_wlock(&rwlock->rwlock);
+    return argv[0];
+}
+
+JANET_CORE_FN(janet_cfun_rwlock_read_release,
+        "(ev/release-rlock rwlock)",
+        "Release a read lock on a read-write lock") {
+    janet_fixarity(argc, 1);
+    JanetAbstractRWLock *rwlock = janet_getabstract(argv, 0, &janet_rwlock_type);
+    janet_os_rwlock_runlock(&rwlock->rwlock);
+    return argv[0];
+}
+
+JANET_CORE_FN(janet_cfun_rwlock_write_release,
+        "(ev/release-wlock rwlock)",
+        "Release a write lock on a read-write lock") {
+    janet_fixarity(argc, 1);
+    JanetAbstractRWLock *rwlock = janet_getabstract(argv, 0, &janet_rwlock_type);
+    janet_os_rwlock_wunlock(&rwlock->rwlock);
+    return argv[0];
+}
+
 void janet_lib_ev(JanetTable *env) {
     JanetRegExt ev_cfuns_ext[] = {
         JANET_CORE_REG("ev/give", cfun_channel_push),
@@ -3086,6 +3148,11 @@ void janet_lib_ev(JanetTable *env) {
         JANET_CORE_REG("ev/lock", janet_cfun_mutex),
         JANET_CORE_REG("ev/acquire-lock", janet_cfun_mutex_acquire),
         JANET_CORE_REG("ev/release-lock", janet_cfun_mutex_release),
+        JANET_CORE_REG("ev/rwlock", janet_cfun_rwlock),
+        JANET_CORE_REG("ev/acquire-rlock", janet_cfun_rwlock_read_lock),
+        JANET_CORE_REG("ev/acquire-wlock", janet_cfun_rwlock_write_lock),
+        JANET_CORE_REG("ev/release-rlock", janet_cfun_rwlock_read_release),
+        JANET_CORE_REG("ev/release-wlock", janet_cfun_rwlock_write_release),
         JANET_REG_END
     };
 
@@ -3093,6 +3160,7 @@ void janet_lib_ev(JanetTable *env) {
     janet_register_abstract_type(&janet_stream_type);
     janet_register_abstract_type(&janet_channel_type);
     janet_register_abstract_type(&janet_mutex_type);
+    janet_register_abstract_type(&janet_rwlock_type);
 }
 
 #endif
diff --git a/src/core/features.h b/src/core/features.h
index 40067414..ce5e3bf1 100644
--- a/src/core/features.h
+++ b/src/core/features.h
@@ -45,9 +45,13 @@
 #define WIN32_LEAN_AND_MEAN
 #endif
 
-/* Needed for realpath on linux */
-#if !defined(_XOPEN_SOURCE) && (defined(__linux__) || defined(__EMSCRIPTEN__))
-#define _XOPEN_SOURCE 500
+/* Needed for realpath on linux, as well as pthread rwlocks. */
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 600
+#endif
+#if _XOPEN_SOURCE < 600
+#undef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 
 /* Needed for timegm and other extensions when building with -std=c99.
diff --git a/src/include/janet.h b/src/include/janet.h
index 9b90a506..3a11a6f5 100644
--- a/src/include/janet.h
+++ b/src/include/janet.h
@@ -299,6 +299,18 @@ typedef struct {
     JANET_CURRENT_CONFIG_BITS })
 #endif
 
+/* Feature include for pthreads. Most feature detection code should go in
+ * features.h instead. */
+#ifndef JANET_WINDOWS
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 600
+#endif
+#if _XOPEN_SOURCE < 600
+#undef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 600
+#endif
+#endif
+
 /* What to do when out of memory */
 #ifndef JANET_OUT_OF_MEMORY
 #include <stdio.h>
@@ -335,9 +347,13 @@ typedef struct JanetDudCriticalSection {
     void *lock_semaphore;
     unsigned long spin_count;
 } JanetOSMutex;
+typedef struct JanetDudRWLock {
+    void *ptr;
+} JanetOSRWLock;
 #else
 #include <pthread.h>
 typedef pthread_mutex_t JanetOSMutex;
+typedef pthread_rwlock_t JanetOSRWLock;
 #endif
 #endif
 
@@ -1368,11 +1384,17 @@ JANET_API void *janet_abstract_threaded(const JanetAbstractType *atype, size_t s
 JANET_API int32_t janet_abstract_incref(void *abst);
 JANET_API int32_t janet_abstract_decref(void *abst);
 
-/* Expose some OS sync primitives to make portable abstract types easier to implement */
+/* Expose some OS sync primitives */
 JANET_API void janet_os_mutex_init(JanetOSMutex *mutex);
 JANET_API void janet_os_mutex_deinit(JanetOSMutex *mutex);
 JANET_API void janet_os_mutex_lock(JanetOSMutex *mutex);
 JANET_API void janet_os_mutex_unlock(JanetOSMutex *mutex);
+JANET_API void janet_os_rwlock_init(JanetOSRWLock *rwlock);
+JANET_API void janet_os_rwlock_deinit(JanetOSRWLock *rwlock);
+JANET_API void janet_os_rwlock_rlock(JanetOSRWLock *rwlock);
+JANET_API void janet_os_rwlock_wlock(JanetOSRWLock *rwlock);
+JANET_API void janet_os_rwlock_runlock(JanetOSRWLock *rwlock);
+JANET_API void janet_os_rwlock_wunlock(JanetOSRWLock *rwlock);
 
 /* Get last error from an IO operation */
 JANET_API Janet janet_ev_lasterr(void);