Index: runtime/src/kmp.h
===================================================================
--- runtime/src/kmp.h
+++ runtime/src/kmp.h
@@ -1058,6 +1058,10 @@
 /* TODO: tune for KMP_OS_HURD */
 #define KMP_INIT_WAIT 1024U /* initial number of spin-tests   */
 #define KMP_NEXT_WAIT 512U /* susequent number of spin-tests */
+#elif KMP_OS_OPENBSD
+/* TODO: tune for KMP_OS_OPENBSD */
+#define KMP_INIT_WAIT 1024U /* initial number of spin-tests   */
+#define KMP_NEXT_WAIT 512U /* susequent number of spin-tests */
 #endif
 
 #if KMP_ARCH_X86 || KMP_ARCH_X86_64
Index: runtime/src/kmp_platform.h
===================================================================
--- runtime/src/kmp_platform.h
+++ runtime/src/kmp_platform.h
@@ -20,6 +20,7 @@
 #define KMP_OS_DRAGONFLY 0
 #define KMP_OS_FREEBSD 0
 #define KMP_OS_NETBSD 0
+#define KMP_OS_OPENBSD 0
 #define KMP_OS_DARWIN 0
 #define KMP_OS_WINDOWS 0
 #define KMP_OS_CNK 0
@@ -61,6 +62,11 @@
 #define KMP_OS_NETBSD 1
 #endif
 
+#if (defined __OpenBSD__)
+#undef KMP_OS_OPENBSD
+#define KMP_OS_OPENBSD 1
+#endif
+
 #if (defined __bgq__)
 #undef KMP_OS_CNK
 #define KMP_OS_CNK 1
@@ -73,12 +79,12 @@
 
 #if (1 !=                                                                      \
      KMP_OS_LINUX + KMP_OS_DRAGONFLY + KMP_OS_FREEBSD + KMP_OS_NETBSD +        \
-         KMP_OS_DARWIN + KMP_OS_WINDOWS + KMP_OS_HURD)
+         KMP_OS_OPENBSD + KMP_OS_DARWIN + KMP_OS_WINDOWS + KMP_OS_HURD)
 #error Unknown OS
 #endif
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
-        KMP_OS_DARWIN || KMP_OS_HURD
+        KMP_OS_OPENBSD || KMP_OS_DARWIN || KMP_OS_HURD
 #undef KMP_OS_UNIX
 #define KMP_OS_UNIX 1
 #endif
Index: runtime/src/kmp_runtime.cpp
===================================================================
--- runtime/src/kmp_runtime.cpp
+++ runtime/src/kmp_runtime.cpp
@@ -7671,7 +7671,7 @@
 #if KMP_ARCH_X86_64 || KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 || KMP_ARCH_MIPS64
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
-    KMP_OS_WINDOWS || KMP_OS_DARWIN || KMP_OS_HURD
+    KMP_OS_OPENBSD || KMP_OS_WINDOWS || KMP_OS_DARWIN || KMP_OS_HURD
 
     int teamsize_cutoff = 4;
 
@@ -7695,7 +7695,7 @@
 #else
 #error "Unknown or unsupported OS"
 #endif // KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD  \
-// || KMP_OS_WINDOWS || KMP_OS_DARWIN
+// || KMP_OS_OPENBSD || KMP_OS_WINDOWS || KMP_OS_DARWIN || KMP_OS_HURD
 
 #elif KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_AARCH || KMP_ARCH_MIPS
 
Index: runtime/src/kmp_wrapper_malloc.h
===================================================================
--- runtime/src/kmp_wrapper_malloc.h
+++ runtime/src/kmp_wrapper_malloc.h
@@ -94,7 +94,7 @@
 #if KMP_OS_WINDOWS
 #include <malloc.h> // Windows* OS: _alloca() declared in "malloc.h".
 #define alloca _alloca // Allow to use alloca() with no underscore.
-#elif KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD
+#elif KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD || KMP_OS_OPENBSD
 // Declared in "stdlib.h".
 #elif KMP_OS_UNIX
 #include <alloca.h> // Linux* OS and OS X*: alloc() declared in "alloca".
Index: runtime/src/z_Linux_util.cpp
===================================================================
--- runtime/src/z_Linux_util.cpp
+++ runtime/src/z_Linux_util.cpp
@@ -22,7 +22,7 @@
 #include "kmp_wait_release.h"
 #include "kmp_wrapper_getpid.h"
 
-#if !KMP_OS_DRAGONFLY && !KMP_OS_FREEBSD && !KMP_OS_NETBSD
+#if !KMP_OS_DRAGONFLY && !KMP_OS_FREEBSD && !KMP_OS_NETBSD && !KMP_OS_OPENBSD
 #include <alloca.h>
 #endif
 #include <math.h> // HUGE_VAL.
@@ -499,7 +499,7 @@
 #endif /* KMP_BLOCK_SIGNALS */
   void *exit_val;
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
-        KMP_OS_HURD
+        KMP_OS_OPENBSD || KMP_OS_HURD
   void *volatile padding = 0;
 #endif
   int gtid;
@@ -547,7 +547,8 @@
   KMP_CHECK_SYSFAIL("pthread_sigmask", status);
 #endif /* KMP_BLOCK_SIGNALS */
 
-#if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD
+#if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
+        KMP_OS_OPENBSD
   if (__kmp_stkoffset > 0 && gtid > 0) {
     padding = KMP_ALLOCA(gtid * __kmp_stkoffset);
   }
@@ -1768,7 +1769,7 @@
   int r = 0;
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
-        KMP_OS_HURD
+        KMP_OS_OPENBSD || KMP_OS_HURD
 
   r = sysconf(_SC_NPROCESSORS_ONLN);
 
@@ -2014,9 +2015,9 @@
     found = 1;
   }
 
-#elif KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD
+#elif KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD || KMP_OS_OPENBSD
 
-  // FIXME(DragonFly, FreeBSD, NetBSD): Implement this
+  // FIXME(DragonFly, FreeBSD, NetBSD, OpenBSD): Implement this
   found = 1;
 
 #else