Norris arrived at Formula 3 off the back of a dominant 2016 junior season in which he won both the Formula Renault 2.0 Eurocup and the Formula Renault 2.0 Northern European Cup with Josef Kaufmann Racing, recording eleven race wins and ten consecutive pole positions in the Northern European Cup. He had also competed in the Toyota Racing Series in New Zealand early in 2016, winning the championship there. By the end of 2016, Norris had received the Autosport BRDC Award — a British motorsport honour recognising the most outstanding young driver of the year.
He joined the McLaren Young Driver Programme in February 2017, giving his junior career an F1-affiliated pathway.
Racing full-time with Carlin in the 2017 European Formula 3 Championship, Norris faced a competitive field that included Joel Eriksson, Maximilian Gunther, and Callum Ilott in contention for the title. The series ran over fifteen rounds, producing thirty races, and Norris was present at the front throughout.
He finished on the podium in twenty of the thirty races, securing nine victories and eight pole positions. The consistency of his scoring was decisive — he did not need to wait until late in the season to build a margin, and he clinched the title with two races still remaining. It was regarded as a comprehensive championship victory against a competitive field.
Norris also made his second appearance at the Macau Grand Prix in November 2017. He qualified second in the race weekend but dropped to seventh in the qualification heat. In the Grand Prix itself, an accident between the leaders on the final lap elevated him to second place behind Dan Ticktum.
The weekend following Macau, Norris made a one-off Formula 2 debut with Campos Racing at the 2017 season finale at the Yas Marina Circuit, replacing Ralph Boschung for the final round. The appearance gave him an early taste of the series ahead of his planned full-season campaign in 2018. Prior to that debut, Norris had stated publicly that Charles Leclerc's 2017 F2 title as a rookie had set the bar: "If I want to beat or prove I'm just as good then I'm going to have to win [the title as a rookie]."
Norris's F3 title was part of a run of British junior-series championships that mirrored the junior career template popularised by Hamilton and later followed by Russell and others. It was the fifth championship of a racing career that had barely begun — he was 17 years old when he clinched it — and it gave McLaren grounds to offer him a Formula One contract for 2019. His Autosport BRDC Award in 2016 was followed by a similar level of recognition for 2017, and by the time he entered Formula 2 in 2018 he was already widely regarded as one of the most complete junior drivers in Europe.
The 2017 F3 field that Norris defeated included multiple future Formula One drivers: Eriksson reached F1 testing, Gunther competed in Formula E, and Ilott raced in F1 and IndyCar. That Norris won the title convincingly — clinching it two rounds early with nine victories — is reflected in the consistency of his subsequent career trajectory.
The 2017 FIA Formula 3 European Championship title remains the headline result of Norris's junior career, representing his transition from a karting and formula-junior prodigy to a proven single-seater champion on the main European stage. It was the final step before Formula 2, where he would finish runner-up to George Russell in 2018, and Formula One with McLaren from 2019. His record of five championships in four junior seasons before the age of 18 has few equivalents in the modern era of driver development.