diff --git a/ORCACDefs/math.h b/ORCACDefs/math.h
index 97008fd..c4c5a54 100644
--- a/ORCACDefs/math.h
+++ b/ORCACDefs/math.h
@@ -227,6 +227,9 @@ long double     tanl(long double);
 double          tanh(double);
 float           tanhf(float);
 long double     tanhl(long double);
+double          tgamma(double);
+float           tgammaf(float);
+long double     tgammal(long double);
 double          trunc(double);
 float           truncf(float);
 long double     truncl(long double);
diff --git a/ORCACDefs/tgmath.h b/ORCACDefs/tgmath.h
index b1336f7..ad2160b 100644
--- a/ORCACDefs/tgmath.h
+++ b/ORCACDefs/tgmath.h
@@ -86,6 +86,7 @@
 #define sqrt(x)         __tg_x(sqrt,(x))
 #define tan(x)          __tg_x(tan,(x))
 #define tanh(x)         __tg_x(tanh,(x))
+#define tgamma(x)       __tg_real_x(tgamma,(x))
 #define trunc(x)        __tg_real_x(trunc,(x))
 
 #endif
diff --git a/Tests/Conformance/c99math.c b/Tests/Conformance/c99math.c
index 369eb0d..0c5f682 100644
--- a/Tests/Conformance/c99math.c
+++ b/Tests/Conformance/c99math.c
@@ -356,6 +356,22 @@ int main(void) {
         expect_approx(erfcl(0.95L), 1.791091927267220e-01L);
         expect_approx(erfcl(9.99L), 2.553157649309533e-45L);
         expect_approx(erfcl(105.0L), 4.300838032791244e-4791L);
+
+        expect_pole_error(tgamma(+0.0), +INFINITY);
+        expect_pole_error(tgammaf(-0.0), -INFINITY);
+        expect_domain_error(tgammal(-2.0));
+        expect_domain_error(tgammal(-15.0));
+        expect_domain_error(tgammal(-1e4900));
+        expect_domain_error(tgammal(-INFINITY));
+        expect_exact(tgammal(+INFINITY),+INFINITY);
+        expect_approx(tgammal(1.0), 1.0);
+        expect_approx(tgammal(6.0), 120.0);
+        expect_approx(tgammal(19.5), 2.77243229863337182e+16L);
+        expect_approx(tgammal(1755.0), 1.979261890105010e+4930L);
+        expect_approx(tgammal(1e-4932L), 1e4932L);
+        expect_approx(tgammal(-0.75), -4.83414654429587774L);
+        expect_approx(tgammal(-50.00001L), -3.2878204666630031e-60L);
+        expect_approx(tgammal(-1753.75L), 1.452754458037161e-4929L);
         
         expect_exact(ceil(+0.0), +0.0);
         expect_exact(ceilf(-0.0), -0.0);
diff --git a/cc.notes b/cc.notes
index 92e41ff..eaf0c1c 100644
--- a/cc.notes
+++ b/cc.notes
@@ -1322,6 +1322,13 @@ long double scalblnl(long double x, long n);
 
 These functions return x * FLT_RADIX^n, computed efficiently.  In ORCA/C, FLT_RADIX is 2.
 
+#include <math.h>
+double      tgamma(double x);
+float       tgammaf(float x);
+long double tgammal(long double x);
+
+These functions compute the gamma function of x.
+
 #include <math.h>
 double      trunc(double x);
 float       truncf(float x);