The Williams FW25 raced during the 2003 Formula One season and was driven by three drivers, Juan Pablo Montoya, Ralf Schumacher and Marc Gene. Gene replaced Schumacher for the Italian Grand Prix after he was involved in an accident during testing at Monza's Lesmo 1 corner prior to that race. Powering the FW25 was a 3-liter BMW V10 powerplant mated to a Williams 7-speed gearbox. It rode on Michelin tires and was fueled by Petrobras fuel.

The FW25 could have won its first Grand Prix - the Australian Grand Prix - but Juan Pablo Montoya spun the car. At the Austrian Grand Prix, Montoya was in the lead prior to engine problems which forced it to retire prematurely.

A new, wider front tire was fitted to the car in preparation for the Monaco Grand Prix, and this helped solve the car's understeer problems. The FW25 finished first at the Monaco GP and scored a double-podium finish at the Canadian grand Prix. It then went on to score a dominant 1-2 victory at the European grand prix at the Nürburgring, and at the French Grand Prix at Magny-Cours.

Protests lodged by Michelin's rivals Bridgestone, through the Ferrari team after the Hungarian Grand Prix forced Williams to switch to a slimmer tire design. Montoya finished in second place at Monza and would not win another race during the final three races of the season.

The team would finish the season in second place in the Contractors' Championship with 144 points.

by Dan Vaughan