A 180° right-handed hairpin taken at approximately 70 km/h — the slowest corner on the modern Spa lap by a significant margin. The approach is downhill from the start–finish line, with cars on cold tyres in the opening lap; the exit launches the cars into a long downhill descent toward Eau Rouge. The combination of a tight low-speed corner immediately followed by a long acceleration zone makes La Source the principal overtaking opportunity on the Spa lap — and the principal first-corner pinch point.
The width of La Source's entry, the slowness of its apex, and the proximity to the start of the lap have produced some of the most-replayed opening-lap incidents in F1 history:
1995 — Damon Hill and Michael Schumacher tangled at La Source on the opening lap, an incident that became part of the long-running personal rivalry between the two drivers.
1998 — In the rain-affected race, David Coulthard lost control approaching La Source, triggering the 13-car first-lap pile-up that destroyed McLaren's championship momentum.
2012 — Romain Grosjean's Lotus launched over Lewis Hamilton's McLaren at the La Source-Eau Rouge transition, taking out Hamilton, Fernando Alonso, Sergio Perez and Grosjean himself in a four-car incident. Grosjean was given a one-race ban — the first first-time race ban in F1 since 1994 — for his role.
2018 — Charles Leclerc was struck on the head by debris from a launched Sauber after a similar opening-lap shunt; the halo cockpit-protection device saved his life. The incident is now the canonical case study for the halo's adoption.
2021 — In the rain-stopped race that produced only formation laps behind the safety car, La Source remained the focal point of the gridded restart that never came.
La Source is the only corner on the modern Spa layout that bears no relation to the original 1922 road circuit. The 1979 reconstruction of Spa from a 14 km road course to the modern 7 km layout required a new start-finish complex; La Source was created from scratch as the slow first corner of the new circuit. The 1922-1969 Spa had no equivalent corner — the original layout began with a long descent toward Burnenville and Masta.
The exit from La Source is the most-discussed setup compromise on the Spa lap. Drivers must choose between:
Early apex — Tightens the line through the hairpin, sacrifices exit speed, but improves defensive position into the Eau Rouge descent.
Late apex — Wider line through the hairpin, costs tenths in the corner itself, but maximises the run through the descent and the slipstream effect into Eau Rouge.
The team's race-engineering staff will set up the differential, throttle map and tyre warm-up routine specifically to favour one or the other strategy, depending on grid position and weather forecast.
La Source is rendered in every Spa sim. The slow hairpin is geometrically straightforward but the entry-braking sequence is one of the standard tests of a sim's brake-balance model — cold tyres on a downhill braking zone, a typical first-lap condition, is a test of how well the sim models tyre temperature and grip transition.