Semriach is a municipality in the district of Graz-Umgebung, in the Austrian state of Styria. It lies in the federal province of Styria in southeastern Austria, within the administrative district that surrounds the city of Graz.
As a municipality, Semriach is one of the local administrative units that make up the Graz-Umgebung district. The district takes its name from Graz, the provincial capital of Styria, which it encircles, though Semriach itself is a separate community with its own municipal government.
Semriach is situated in the Alpine foothills region of Styria. The surrounding area is known for its karst landscape, including cave systems such as the Lurgrotte, a show cave that extends through the limestone near the municipality. The village serves as a local residential and administrative centre for its surrounding rural area.