El Horno Creek or Horno Creek (Spanish: "Oven Creek") is a tributary stream of San Juan Creek in Orange County in the U.S. state of California. It is approximately 5.9 miles (9.5 km) long and drains an area of 4.3 square miles (11 km²). The creek joins San Juan Creek on the right bank, only a few hundred yards upstream of the Trabuco Creek confluence, within the city limits of San Juan Capistrano. The creek begins in the foothills of the Santa Ana Mountains (33.5672464°N 117.6300495°W), a mountain range that occupies most of the west half of the San Juan watershed. There is a significant amount of single-family residential development there, and the creek is mostly inside an underground storm channel. It flows south and southwest before turning west under Interstate 5, where it enters a channelized course and parallels the interstate to its discharge point at San Juan Creek, also from a subterranean culvert (33.4978044°N 117.6553283°W).