Venus Williams made her debut on the WTA Tour as a 14-year-old in 1994American veteran Venus Williams beat a top-20 player for the first time in four years with victory over Russia's Veronika Kudermetova in Cincinnati.
Williams, 43, fought back from a double break down in each set to win 6-4 7-5 against 16th-ranked Kudermetova.
The seven-time major singles champion smiled broadly as she celebrated winning at a US tournament for the first time in more than three years.
"I love this game, it's what I do," said Williams, who is ranked 533rd.
"The last few years have been difficult in terms of injuries but I love to be out here, be strong and be myself. I'm getting there."
Williams will play China's Qinwen Zheng or Belarus' Aliaksandra Sasnovich in the second round.
The former world number one will look to win back-to-back matches on the WTA Tour for the first time since the 2019 event in Cincinnati.
That was also the tournament when she last won against a top-20 opponent, beating then world number five Kiki Bertens on her way to the quarter-finals.
Later on Monday, Wimbledon champion Marketa Vondrousova plays fellow Czech Katerina Siniakova, while Danish former number one Caroline Wozniacki continues her comeback after retirement against France's Varvara Gracheva.
Wozniacki was supposed to face Ukraine's Elina Svitolina, but the Wimbledon semi-finalist - who has also recently returned to the tour after having a baby - pulled out with a foot injury.
In the men's draw, British number two Dan Evans plays Italy's Lorenzo Musetti in his opening match.
The Western and Southern Open in Cincinnati is one of the key tournaments on the American hard-court swing which culminates at the US Open.
The final Grand Slam event of the season starts in New York on 28 August.
British women's number two Jodie Burrage, who has direct entry for the main draw at Flushing Meadows, continued her preparations with a 6-4 6-2 win over Russian fifth seed Diana Shnaider at the Golden Gate Open.
But Heather Watson lost 6-2 6-4 to Belarusian Iryna Shymanovich at the Californian event.
