Liu Qiangdong, the founder of e-commerce giant JD.com, and his wife, Zhang Zetian, were among guests at Windsor Castle on Friday as the royal married her fiance, Jack Brooksbank.
The couple were making their first appearance in public since Mr Liu was arrested in Minneapolis in August on suspicion of rape.
Minnesota prosecutors are currently considering whether to pursue formal charges against the businessman, also known as Richard Liu, but have set no deadline for a decision.
Mr Liu has denied the allegations made against him and a US-based lawyer representing him said earlier this month he did not expect the billionaire to be charged.
Several influencers on Chinese social media platform Weibo drew attention to the couple’s appearance at the royal wedding following the ceremony.
Many of the posts asserted Mr Liu’s innocence or concluded he and his wife had now put the scandal behind them.
However, others on the site voiced suspicion over the outpouring of support for the billionaire, claiming some of the posts were part of a paid PR campaign.
“Good job manipulating public opinion,” one user replied to a popular post from an influencer about Mr Liu and Ms Zhang.
Meanwhile, Mr Liu’s invitation to the service was also condemned on Douban – another Chinese social network.
“I’d like to know why the royal family let them into the wedding. He has a case against him,” one user wrote.
The Royal Household told The Independent it would not comment on individual guests who had attended the wedding.
Princess Eugenie married Mr Brooksbank in a ceremony at St George’s Chapel in Windsor Castle, the same venue that hosted the wedding of the Duke and Duchess of Sussex five months ago.
A host of celebrities attended the service, including Hollywood actress Demi Moore, supermodel Kate Moss and artist Tracey Emin, while more than 40 royals were also handed invitations.
Mr Liu is the chief executive of JD.com - China’s second biggest online retailer after the Alibaba Group - and is thought to be worth around $12.7bn (£9.60bn).
The company boasts tech firm Tencent and US grocery chain Walmart among its major investors.
The internet entrepreneur has in recent months moved to distance himself from a second scandal, in which a guest at a dinner party he was hosting sexually assaulted a woman.
Xu Longwei was jailed for two-and-a-half years in Australia last week for attacking the woman in a Sydney hotel room after plying her with alcohol at the private event.
The sentencing judge clarified Mr Liu had played no part in the offences after the billionaire was denied a court order to prevent release of his name in connection with the case.
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