diff --git a/libclc/generic/include/clc/clc.h b/libclc/generic/include/clc/clc.h
index 45b107cb86a3..0fc8530e9949 100644
--- a/libclc/generic/include/clc/clc.h
+++ b/libclc/generic/include/clc/clc.h
@@ -32,6 +32,7 @@
 #include <clc/workitem/get_group_id.h>
 
 /* 6.11.2 Math Functions */
+#include <clc/math/acos.h>
 #include <clc/math/atan.h>
 #include <clc/math/atan2.h>
 #include <clc/math/copysign.h>
diff --git a/libclc/generic/include/clc/math/acos.h b/libclc/generic/include/clc/math/acos.h
new file mode 100644
index 000000000000..e753dee36aa5
--- /dev/null
+++ b/libclc/generic/include/clc/math/acos.h
@@ -0,0 +1,2 @@
+#define __CLC_BODY <clc/math/acos.inc>
+#include <clc/math/gentype.inc>
diff --git a/libclc/generic/include/clc/math/acos.inc b/libclc/generic/include/clc/math/acos.inc
new file mode 100644
index 000000000000..4ca8c7538aef
--- /dev/null
+++ b/libclc/generic/include/clc/math/acos.inc
@@ -0,0 +1 @@
+_CLC_OVERLOAD _CLC_DECL __CLC_GENTYPE acos(__CLC_GENTYPE x);
diff --git a/libclc/generic/lib/SOURCES b/libclc/generic/lib/SOURCES
index 22fc1fb22920..577671cc216c 100644
--- a/libclc/generic/lib/SOURCES
+++ b/libclc/generic/lib/SOURCES
@@ -29,6 +29,7 @@ integer/sub_sat.cl
 integer/sub_sat_if.ll
 integer/sub_sat_impl.ll
 integer/upsample.cl
+math/acos.cl
 math/atan.cl
 math/atan2.cl
 math/copysign.cl
diff --git a/libclc/generic/lib/math/acos.cl b/libclc/generic/lib/math/acos.cl
new file mode 100644
index 000000000000..3ce96554fef3
--- /dev/null
+++ b/libclc/generic/lib/math/acos.cl
@@ -0,0 +1,8 @@
+#include <clc/clc.h>
+
+#ifdef cl_khr_fp64
+#pragma OPENCL EXTENSION cl_khr_fp64 : enable
+#endif
+
+#define __CLC_BODY <acos.inc>
+#include <clc/math/gentype.inc>
diff --git a/libclc/generic/lib/math/acos.inc b/libclc/generic/lib/math/acos.inc
new file mode 100644
index 000000000000..8612415f37bd
--- /dev/null
+++ b/libclc/generic/lib/math/acos.inc
@@ -0,0 +1,21 @@
+/*
+ * There are multiple formulas for calculating arccosine of x:
+ * 1) acos(x) = (1/2*pi) + i * ln(i*x + sqrt(1-x^2)) (notice the 'i'...)
+ * 2) acos(x) = pi/2 + asin(-x) (asin isn't implemented yet)
+ * 3) acos(x) = pi/2 - asin(x) (ditto)
+ * 4) acos(x) = 2*atan2(sqrt(1-x), sqrt(1+x))
+ * 5) acos(x) = pi/2 - atan2(x, ( sqrt(1-x^2) ) )
+ *
+ * Options 1-3 are not currently usable, #5 generates more concise radeonsi
+ * bitcode and assembly than #4 (134 vs 132 instructions on radeonsi), but
+ * precision of #4 may be better.
+ */
+
+_CLC_OVERLOAD _CLC_DEF __CLC_GENTYPE acos(__CLC_GENTYPE x) {
+  return (
+    (__CLC_GENTYPE) 2.0 * atan2(
+      sqrt((__CLC_GENTYPE) 1.0 - x),
+      sqrt((__CLC_GENTYPE) 1.0 + x)
+    )
+  );
+}