San Martin Airport (formerly South County Airport of Santa Clara County, colloquially South County Airport) (FAA LID: E16) — formerly Q99 — is a public non-towered airport located 1 mi (1.6 km) east of San Martin, serving Santa Clara County, California, United States. This general aviation airport covers 179 acres (72 ha) and has one runway. A self-service fueling facility offers 94UL aviation gasoline (not 100LL) continuously. Jet-A fuel is available from a full-service truck during FBO operating hours, and major airframe and powerplant service are available. San Martin Aviation is the fixed-base operator (FBO) at South County, serving aviation fuels and aircraft & hangar maintenance.

Although still distinctly visible from the air and shown on some maps, taxiway "F", adjacent to the U.S. Route 101 fence, has been abandoned and decommissioned since about 2000.

The Wings of History Air Museum is located adjacent to the airport.