The 64-year-old has been in negotiations with the club for some time and will now be part of the setup at the Premier League outfit.
It has been claimed by The Telegraph that Gao has bought the stake - believed to be worth in the region of £210m - as an individual rather than through his company Lander Holdings, and Liebherr will remain part of the ownership structure.
Liebherr said in a statement on the Southampton website: "I am pleased to confirm that talks to bring in a new partner to our club have been concluded. Following extensive and fruitful work, we are entering into a partnership with the Gao family and I am excited about what we will achieve together.
"Today is the start of a new and exciting chapter for our club. Mr Jisheng Gao and his daughter, Mrs Nelly Gao, with whom I have built a close relationship, share our values and ambitions. As a team, we will strive to build upon the strong foundation that is in place towards sustainable long-term success.
"Mr Gao, Nelly and I have full trust in Ralph Krueger and his management team. We wholeheartedly support their plans to follow the Southampton Way in the years ahead. But for now it is business as usual at Southampton Football Club and we must allow everyone at the club to focus on the first few weeks of the new season."
Jisheng Gao, meanwhile, added: "I am honoured and humbled to become a partner of Southampton Football Club alongside Katharina Liebherr, who, together with her father, has been such a great steward of the club, its growth and success. Together, we have the passion and motivation to build on Southampton's excellent progress in recent years as we look forward to an exciting next chapter for the club."
A number of leading English clubs, such as West Bromwich Albion, Aston Villa, Wolverhampton Wanderers and Birmingham City, have been bought by Chinese investors over the last few years.