Four-time major winner Naomi Osaka said her first-round win over Italy's Lucia Bronzetti at the French Open was "like a rollercoaster".

Japan's Osaka came through 6-1 4-6 7-5 for her first victory at Roland Garros in three years.

The victory could have been swifter for Osaka, who led 4-0 in the third set before Bronzetti mounted a late challenge.

The former world number one is playing in just her second major since returning from maternity leave in January.

"It really was like a rollercoaster," said Osaka, who lost in the first round of the Australian Open on her Grand Slam return.

"I was in my head, thinking I didn't win a match in Australia so I'd really love to win one here. Obviously that wasn't a good train of thought."

Her win in Paris sets up a likely second-round meeting with defending champion and heavy title favourite Iga Swiatek, who takes on France's Leolia Jeanjean on Monday.

Osaka said she watched Swiatek play a lot when she was pregnant, adding it would be a "big honour" to play the current world number one.

"I definitely do feel like it's a test to see where I'm at, but I wouldn't say I have low expectations of myself," she said.

"I feel like I'm the underdog, and I think I thrive in those situations."