Coco Gauff takes down Venus Williams in the first round in straight sets, 7-6, 6-3, for her first career win at the Australian Open. (2:31)

MELBOURNE, Australia -- Everyone had the same question before the Australian Open draw was revealed: What were the odds that Coco Gauff and Venus Williams would face each other again in the first round at a Grand Slam tournament?

"I was a bit shocked," Gauff said. "I'm sure everyone was a bit shocked."

Gauff, 15, played Williams, 39, to begin her first appearance in the main draw at Melbourne Park, as she did at Wimbledon last year. Just like at the All England Club, the youngest woman in the field got the better of the oldest woman in the field, with Gauff beating Williams 7-6 (5), 6-3 on Monday.

"That was really difficult. She played really well," Gauff said. "I was really nervous."

It was the most anticipated match of Day 1 at the first major tennis tournament of the year, and it did not disappoint. The first set, in particular, was intriguing, with Gauff repeatedly pulling ahead, only to have Williams -- who won four of her seven Grand Slam singles trophies before Gauff was born -- rebuff her.

It wasn't until her fourth set point that Gauff finally prevailed, and she then grabbed a 3-0 lead in the second set and never let that edge go.

"I definitely was more confident this time. I think I was used to playing on big courts, so the crowd -- I guess the size of the crowd didn't startle me as much as last time," Gauff said. "Definitely a bit more positive coming into this match."

Gauff has already demonstrated all sorts of terrific qualities on the tennis court, from her big, gutsy serves to her ability to track down opponents' shots. We can now add stick-to-it-iveness to the list.

The match was held in Margaret Court Arena, one of three stadiums in Melbourne with a retractable roof, and that was a good thing. For all of the concern entering the tournament about air quality because of wildfires burning in parts of the country, the big issue Monday was a heavy storm that arrived in the afternoon and suspended play on outside courts for hours.

Among the other women who got a chance to play -- and win -- were defending champion Naomi Osaka, 23-time major champion Serena Williams, local favorite and top-ranked Ash Barty and 2018 Australian Open winner Caroline Wozniacki, who is retiring after this Australian Open.

For something new, Osaka's father, Leonard Francois, was in the crowd watching as she reeled off the last four games after dropping serve for the only time to beat Marie Bouzkova 6-2, 6-4.

Next up, Serena Williams started her bid for her record-tying 24th Grand Slam singles title when she beat 18-year-old Anastasia Potapova 6-0, 6-3. Williams has won the title seven times in Australia and is now aiming for her first major title since giving birth. She hasn't added to her Grand Slam tally since her victory at the 2017 Australian Open. She ended one drought last week, when she won the title in Auckland, New Zealand, marking her first since the Australian title three years ago.

"I hadn't been able to win as a mom, so it was nice to finally be able to win a tournament with a 2-year-old now," Williams said of her Auckland win. "I've been pretty close, but it was special for me and for her. I hope for her."

Williams has made it to -- but lost -- four Grand Slam finals since her most recent title and is determined to end that streak.

She won seven straight games until Potapova held serve and changed the momentum -- for a little while. Potapova got a service break, but Williams rallied quickly to get back on track.

Osaka thanked the crowd after her match, saying, "You probably didn't come for me, but thanks for filling up the stadium."

There was one person who was there for only Osaka.

"My dad watched my match from my box for the first time during a Grand Slam," tweeted Osaka, who won back-to-back majors at the 2018 US Open and 2019 Australian Open. "I feel so happy."

She later explained: "He's just superstitious. Because, like, he literally -- because, like, before when he used to sit in my box, I would just look at him and complain a lot, but I have matured over the past, like, three or four years he hasn't sat in my box."

Osaka is aiming to become the ninth woman to successfully defend an Australian Open title. She wasn't able to do that at the US Open last year, when she lost in the fourth round, but she says she learned some valuable lessons.

"Definitely, it was really tough for me trying to control my nerves," she said of her first-round win. "I'm really glad I was able to finish it in two."

Barty got off to a slow start in her home tournament, dropping the first set before quickly grabbing the second two en route to a 5-7, 6-1, 6-1 victory over Lesia Tsurenko.

Wozniacki beat Kristie Ahn 6-1, 6-3 in the last tournament of the former No. 1's professional career. Wozniacki, 29, has announced that she will retire after the Australian Open, where she won her first major title in 2018.

Two-time Wimbledon winner Petra Kvitova is also through to the second round after beating Katerina Siniakova 6-1, 6-0. Kvitova lost the final to Osaka last year.

Other seeded players advancing on the women's side included No. 13 Petra Martic and No. 14 Sofia Kenin. Martic had a 6-3, 6-0 win over Christina McHale, and Kenin beat Italian qualifier Martina Trevisan 6-2, 6-4.

The Associated Press contributed to this report.