The Hirtenberg HS.9 was an Austrian two-seat touring or training aircraft of the early 1930s.
A derivative of the Hopfner HS-5/28 via the Hopfner HS-8/29, the HS.9 was a parasol wing monoplane with a fixed tailskid landing gear and room for two occupants in tandem open cockpits, and first flew as the Hopfner HS-9/32 in 1932, powered by a de Havilland Gipsy I engine. Production versions had Siemens Sh 14 engines with NACA cowlings. A single example of a refined version with an uncowled Siemens engine was flown in 1935 as the Hopfner HS-9/35, shortly before the Hopfner company went bankrupt.
When Hopfner's assets were purchased by Otto Eberhardt Patronenfabrik, production continued of both de Havilland- and Siemens-powered aircraft under the Hirtenberg brand.