The season took place during a period of significant manufacturer competition. Citroën had entered the WRC in force the previous year and came into 2003 as the team to beat, with Sébastien Loeb and Carlos Sainz as their lead drivers. Peugeot remained competitive. Subaru provided the main challenge from the Japanese manufacturers, with Petter Solberg and Richard Burns leading their campaign.
A calendar change saw the Safari Rally Kenya dropped from the schedule due to unresolved fee payments from previous seasons. The event was replaced by the Rally of Turkey, which made its WRC debut as a championship round.
The championship came down to a straight fight between Petter Solberg and Sébastien Loeb. Loeb won three events across the season — the Monte Carlo Rally, Rallye Deutschland, and Rallye Sanremo — and was widely regarded as the faster driver throughout. However, Citroën, mindful of their manufacturers' title ambitions, instructed Loeb not to chase Solberg at all costs in the final rounds to avoid compromising the team's standings. As a result, Loeb entered the season finale, the Wales Rally Great Britain, needing to beat Solberg. Solberg won in Wales, securing the drivers' championship title by a single point over Loeb — one of the closest margins in WRC history.
Loeb's defeat came despite him having outperformed more illustrious teammates Carlos Sainz and Colin McRae across the season, which significantly raised his profile and established him as the dominant force entering 2004.
Citroën won the manufacturers' title, their first, securing it in Wales. They finished ahead of Peugeot and Subaru. Citroën's success reflected their total commitment to the WRC that year, with both Loeb and Sainz contributing points consistently across the calendar.
Petter Solberg took his only WRC drivers' title this season, driving for Subaru. His victory in Wales to clinch the championship was the decisive result. Carlos Sainz, driving for Citroën, finished third in the drivers' standings. Richard Burns, also in a Subaru, had a difficult season by comparison.
The season also featured separate support classes — the Junior World Rally Championship (JWRC) for two-wheel-drive cars and the Production Car World Rally Championship (PWRC) for lightly modified production vehicles — both of which ran as categories within the main event at each round, with their own standings.
The 2003 season was the last time Sébastien Loeb did not win the drivers' championship until his retirement from full-time WRC participation after 2012. From 2004 through 2012, Loeb won nine consecutive titles, beginning his record-breaking run immediately after the one-point defeat in Wales. The closeness of the 2003 result — and the circumstances of team orders that may have cost Loeb the title — gave the 2003 season a particular historical resonance as the moment before the longest period of domination by a single driver in the championship's history.