Simona Halep of Romania suffered a shock first round exit at the US Open ©Getty Images

Two-time Grand Slam champion Simona Halep of Romania suffered a shock first round exit as Britain's Sir Andy Murray started with a win on the 10th anniversary of his US Open victory and Serena Williams also tasted victory in what is expected to be her final major.

Halep, the Romanian seventh seed went down to Ukraine’s Daria Snigur, who was making her Grand Slam main-draw debut.

The 20-year-old won 6-2, 0-6, 6-4.

Williams, who is set to retire after the US Open, broke Montenegro's Danka Kovinić five times en route to a 6-3, 6-3 win.

Estonia's Anett Kontaveit, seeded second, awaits for American great Williams.

Williams has won 23 Grand Slam singles titles, including six victories in New York City.

Canada's 2019 champion Bianca Andreescu of Canada prevailed in three sets against Harmony Tan of France.

After a 6-3, 3-6, 6-1 win, Andreescu will be up against Brazil's Beatriz Haddad Maia in the next round.

It took only one hour for Haddad Maia to dismantle Croatia’s Ana Konjuh 6-0, 6-0.

Greek third seed Maria Sakkari got the better of Germany’s Tatjana Maria in three sets, winning 6-4, 3-6, 6-0, before home star Coco Gauff won in straight sets against France’s Leolia Jeanjean 6-2, 6-3.

Serena Williams made a winning start at what is expected to be her final US Open ©Getty Images
Serena Williams made a winning start at what is expected to be her final US Open ©Getty Images

In the men's singles, defending champion Daniil Medvedev started with a bang as he ousted America Stefan Kozlov 6-2, 6-4, 6-0 at the Arthur Ashe Stadium.

Medvedev, who is Russian, is playing as a neutral, having been prevented from competing at Wimbledon.

Former world number one Murray beat Argentine 24th seed Francisco Cerundolo 7-5, 6-3, 6-3.

Italian star Matteo Berretini also triumphed in straight sets as he beat Chile’s Nicolas Jarry 6-2, 6-3, 6-3.

Greece's Stefanos Tsitsipas was the most high-profile casualty.

The fourth seed succumbed to a 6-0, 6-1, 3-6, 7-5 loss against Colombian qualifier Daniel Galán, never recovering from a terrible start which saw Tsitsipas win only seven points in the frst set.

Wu Yibing created history as he became the first Chinese man to win a a Grand Slam singles match in 63 years.

He beat Georgia’s world number 35 Nikoloz Basilashvili 6-3, 6-4, 6-0.

Tim van Rijthoven came back from after being two sets down to win against China’s Zhang Zhizhen 3-6, 6-7, 7-6, 6-1, 6-4.

Sebastian Korda of the United States beat Argentine Facunda Bagins 5-7, 7-6, 7-5, 6-1.