Carlos Sainz Vázquez de Castro was born in Madrid, Spain, on 1 September 1994, as the son of Carlos Sainz Cenamor and Reyes Vázquez de Castro. Carlos has two sisters.
Carlos Sainz started his karting career in 2006 in the minis and cadets. He finished third in the 36th edition of the Torneo Industry and second in the Copa Campeones Trophy. In 2008 he won the CIK-FIA Asia-Pacific championship for Vortex in the KF3 championship. In 2009 he won the thirteenth edition of the CIK FIA KF3 Monaco Kart Cup.
In 2010 he switched to the single-seaters. During his debut year, Sainz drove in various Formula BMW classes. He achieved several victories and finished fourth in the Formula BMW Europe Championship. In 2011 he won the Formula Renault 2.0 NEC Championship title for Koiranen Motorsport. With seventeen podiums, including ten wins, he was ahead of Daniil Kvyat, Stoffel Vandoorne and Robin Frijns. He finished fifth in the 2012 European Formula 3 Championship with six podiums.
In 2013 he was appointed by Red Bull as its test driver for Toro Rosso and Red Bull Racing. In the same year he raced in GP3 and Formula Renault 3.5. It turned out to be an unsuccessful year. In 2014 he won the Formula Renault 3.5 championship title by staying ahead of Pierre Gasly. With seven wins and seven pole positions, he became champion.
In 2015 he made his debut in Formula 1. After the loss of Jean-Eric Vergne and the transfer of Daniil Kvyat to Red Bull Racing, Carlos Sainz became the teammate of Max Verstappen. In his first year he finished sixth at the Circuits of the Americas. In 2016 Sainz developed as a regular points finisher and scored 46 points. Towards the end of the 2017 season, he switched to Renault. For the French stable, he scored his best result for Renault in Baku 2018. For Toro Rosso, he finished fourth at the 2017 Singapore rain race. Ahead of the 2019 season, he took over the seat of Fernando Alonso at McLaren.