The Australian's hopes of a big result at the Roxy Pro France hit early trouble on Thursday night (AEST) when she finished last in her opening-round heat.

That puts the seven-time world champion into a round-two heat against compatriot Nikki Van Dijk and Paige Hareb of New Zealand.

Australian Keely Andrew had an upset win and French surfer Johanne Defay outscored Gilmore to relegate the star to last in their heat.

It will be Gilmore's first time in the second round since Bells Beach last year, which she went on to win.

The Roxy Pro is the third-last event in the World Surf League and Gilmore is fourth in the rankings behind Americans Carissa Moore and Lakey Peterson and fellow Australian Sally Fitzgibbons.

Gilmore only has one event win so far this year as she aims for a record eighth world title, but the Australian has made at least the quarter-finals in the other six rounds.

She is also bidding to secure one of the two Australian selections when surfing makes its Olympics debut next year in Tokyo.

Gilmore was the only women among the top four to slip up in round one, with Fitzgibbons winning her heat and the two Americans taking second places to also advance into the third round.

Brazil's two-time defending world champion Gabriel Medina won his round-one heat in three- to five-feet surf at the back-up site of Les Culs Nus.

Australian Owen Wright, the world No.7, also won through to round three, as did ninth-ranked compatriot Julian Wilson and American legend Kelly Slater.

Organisers have called a lay day for Friday night (AEST).

Australian Associated Press