The chassis was designed by Mike Gascoyne, Bob Bell, Tim Densham, and John Iley, with Pat Symonds overseeing engineering as executive director and Jean-Jacques His leading engine design. The car was simply named R23 to reflect the team's clean break from its Benetton heritage.
The most notable technical experiment of the R23's development cycle was the RS23 engine, which used an unconventional 111-degree vee angle between its ten cylinders — a configuration intended to lower the engine's centre of gravity and improve handling balance. The concept showed promise in theory but proved too unreliable and heavy in practice, and Renault reverted to a more conventional 72-degree vee angle for the following season's R24.
A revised B-specification car, the R23B, debuted at the British Grand Prix and was used for the remainder of the season, bringing aerodynamic improvements that contributed to stronger results in the second half of the year.
The car was launched in January 2003 at an official ceremony in Lucerne, Switzerland, with primary sponsor Mild Seven confirmed, before the car was shown again at Paul Ricard in France — a double-launch arrangement necessitated by French advertising restrictions on tobacco.
Both drivers scored points at the opening round in Australia. In Malaysia, Alonso took pole position, becoming both the youngest driver and the first Spaniard to claim pole in Formula One at that time, before finishing third for his maiden Formula One podium. He followed that with another third place in Brazil, where the race was disrupted by a major accident involving Mark Webber's Jaguar.
While Trulli's form became inconsistent through the season, Alonso continued scoring regularly, including a career-best second place at the Spanish Grand Prix. Following a double retirement in France, Renault introduced the R23B upgrade at the British Grand Prix. The updated car gave Trulli a third place at the German Grand Prix weeks later.
The season's defining moment came at the Hungarian Grand Prix, where Alonso won the race. The victory made him the youngest Formula One race winner since Bruce McLaren had achieved the same distinction 44 years earlier. It was also the first win for a Spanish driver in Formula One history, and Renault's first outright victory as a constructor since 1983.
The final three races brought one additional point for Alonso and two modest finishes for Trulli. In total, the R23 and R23B carried Renault to fourth in the Constructors' Championship with 88 points.
The Hungarian Grand Prix win stands as the R23's enduring legacy event: Alonso at 22 years old, delivering Renault their first triumph as a full constructor in twenty years. The dual-specification campaign — original car to mid-season, then B-spec — was a sign of Renault's technical ambition and organisational capability, even if the exotic engine architecture ultimately did not deliver as hoped.
Heikki Kovalainen drove his first Formula One test in a Renault R23 at the Circuit de Catalunya in December 2003, marking an early connection between the Finnish driver and the team that would later sign him.
The R23 season established Renault as a serious championship contender and confirmed Alonso as a driver of rare talent. The lessons drawn from the 111-degree engine experiment were applied constructively to the R24, and the partnership between Alonso and the Renault technical group deepened into the championship-winning campaigns of 2005 and 2006.