Ahead of the 2017 season, Pier Guidi signed a factory contract with
Ferrari. It would soon be announced that he was replacing
Gianmaria Bruni at
AF Corse's LMGTE Pro outfit in the
FIA World Endurance Championship, where he paired up with
James Calado. The year unraveled in triumphant fashion, as seven podiums from nine races, including wins at the
Nürburgring,
Austin, and
Fuji gave Pier Guidi and Calado their first world championship. Pier Guidi and Calado returned with AF Corse for the
2018–19 WEC 'Super-Season'. They were unable to defend their title, though a class victory at the
2019 24 Hours of Le Mans and a win at
Silverstone guaranteed the duo second in the standings. Another season without a championship followed in
2019–20, where a lone win at
Shanghai resulted in fifth and sixth place for Calado and Pier Guidi - the Italian having missed the final race. The year did not pass without individual success for Pier Guidi however, as he won the
GT World Challenge Europe Endurance Cup driving a
Ferrari 488 GT3. With
Aston Martin exiting the WEC after 2020, leaving only two manufacturers in the GTE Pro class,
2021 proved to be a season-long battle between the #51
AF Corse Ferrari of Pier Guidi and Calado and the No. 92
Porsche of
Kévin Estre and
Neel Jani. Porsche drew first blood by utilising fuel strategy to win at
Spa-Francorchamps, with Ferrari countering with a win in the
Algarve. Despite voices in the Porsche camp suggesting that Ferrari would have the advantage going into the
6 Hours of Monza, Estre and Jani proved to be victorious, as a chasing Pier Guidi had to pit for fuel with a few laps to go. This disappointment would be turned into glory at
Le Mans, where Pier Guidi, Calado, and
Côme Ledogar won after dominating the latter half of the race. The final two races, both held at
Bahrain, began with Porsche taking a dominant win at the
6 Hour event, moving a mere point behind Pier Guidi and Calado, a gap that turned into a dead heat once Porsche had scored pole for the
8 Hour round. During the finale, controversy reigned supreme, as Pier Guidi made contact with the class-leading No. 92 Porsche of
Michael Christensen 12 minutes from the end of the race, who changed racing line while breaking after a failing attempt to block an LMP2 car, spinning around his title rival and inheriting first place. The stewards ordered Pier Guidi to return the place to Christensen, though as the Italian slowed on the main straight, the Porsche went into the pits to refuel the car. Pier Guidi, who pitted for fuel a lap later, came out ahead of Christensen and did not make another attempt to give back the position, and he was also not obliged to do so by the stewards, crossing the line in first and winning the championship. After Porsche protested the stewards' decision to let the win stand, an official appeal was swiftly withdrawn, thus confirming Pier Guidi and Calado as two-time champions. During the year, the Italian also scored a personal achievement at the
24 Hours of Spa, winning the race for
Iron Lynx with a late overtake on the leading
Audi of
Dries Vanthoor. This result helped Pier Guidi to retain the
GTWC Europe Endurance Cup crown, one he shared with
Nicklas Nielsen and
Côme Ledogar. at the
2022 24 Hours of Le Mans For 2022, Pier Guidi and Calado returned to defend their title in what would end up being the final year of the LMGTE Pro category in the
WEC. Pier Guidi impressed throughout the year, scoring the marque's sole pole at
Monza, putting in important stints at
Spa in challenging weather conditions and winning the races in Belgium and
Fuji, though his finest drive came at the final round in
Bahrain. There, the car, which had initially looked likely to score a podium, developed a gearbox issue with two hours remaining which dropped them behind all other GTE Pro runners. Pier Guidi, using only fifth gear for the majority of his final stints, brought the car home ahead of the GTE Am cars, which were eligible for GTE points, in fifth, thereby winning the championship for a third time.
Ferrari entered the
Hypercar class for the
2023 WEC season, fielding two
Ferrari 499P in an alliance with
AF Corse. Pier Guidi would be placed in the No. 51 car, remaining alongside Calado and being joined by
Antonio Giovinazzi. The opening round at
Sebring proved to be a disappointment, as Pier Guidi collided with a GTE Am Ferrari and finished seventh, meanwhile a brake issue forced the Italian to nurse the car home in sixth at
Portimão. At
Spa, the trio achieved their first podium of the year, with Calado overtaking Porsche's
Frédéric Makowiecki on the final lap to snatch third place.
Le Mans became the season's magnum opus: After Ferrari locked out the front row with Pier Guidi starting behind poleman
Antonio Fuoco, the No. 51 crew got into the lead by nightfall, though a spin into the gravel by Pier Guidi forced them to be recovered by a recovery vehicle, dropping them to fourth near midnight. The team remained undeterred and got back into the lead at the halfway mark, going on to control the race well into the morning. Despite a late challenge by
Toyota, a spin caused them to fall back, leaving Pier Guidi to cross the line to win the centenary edition of the 24 Hours and bringing Ferrari their first overall Le Mans win in 50 years. This result turned out to be the final podium for the No. 51 trio, who finished fourth in the standings, one place behind their teammates in the No. 50. == Racing record ==