 Montagny had a breakthrough year in Formula Three in 1998, including a pole position at the Spa-Francorchamps race ahead of much more experienced drivers including Mark Webber, Luciano Burti, Enrique Bernoldi and Peter Dumbreck.He repeated the feat in the Zandvoort Masters in the Netherlands later that year, beating then German Formula Three champion Nick Heidfeld.He consistently outpaced long-time teammate Sébastien Bourdais and ended the season with 10 wins from 22 races, including 12 pole positions, finishing the championship as runner-up behind David Saelens.