The Wildflower Triathlon is a triathlon held at Lake San Antonio in Central California since 1983. It is held the first weekend in May each year. Wildflower is known all over the world for its festival like atmosphere, challenging courses and some of the most energetic collegiate volunteers. It has been named "the woodstock for triathlon", "the best of the best", "triathlon back to the basic roots", "elites favorite race", and more.  It's the "one and only" wildflower as there is nothing else like it in the world.

The original course was expanded to the standardized half-Ironman distance (1.9 km / 90 km / 21.1 km) in the late 1980s, and is often referred to as simply the long course. Two more races have subsequently been added to the event: an Olympic-distance (1.5 km / 40 km / 10 km) race and a short or "sprint" mountain-bike triathlon (0.4 km / 15.6 km / 3.2 km). 

Known for a particularly hilly and grueling course, it is one of the largest triathlon events in the world, with 7,500 athletes and 30,000 spectators attending each year at its peak. Traditionally it is associated with a Wildflower festival, though in recent years the festival had been eclipsed by the increasingly large athletic event.