Apax Partners LLP is a British private equity firm, headquartered in London, England. The company also operates out of six other offices in New York, Hong Kong, Mumbai, Tel Aviv, Munich and Shanghai. As of March 2024, the firm had raised and advised funds of approximately US$77 billion. Apax Partners is one of the oldest and largest private equity firms operating on an international basis.

Apax invests across three sectors: technology, internet/consumer and services. It looks for investments in a target Enterprise Value of $100–5,000 million.

Apax raises capital for its investment funds through institutional investors including corporate and public pension funds, university and college endowments, foundations and fund of funds.

In 1972, Ronald Mourad Cohen and Maurice Tchénio founded the advisory firm Multinational Management Group (MMG) in London, Paris, and Chicago, marking the beginning of Apax Partners. In 1977, they formed a partnership with early venture capitalist Alan Patricof, who founded Patricof & Co in New York in 1969. The new firm would be known as Alan Patricof Associates (APA) and ultimately come to be known as Apax Partners (apax means "unique" in classical Greek).

Throughout the 1980s, the firm grew steadily raising capital under a series of separate funds.

In 1991, Apax Partners became the official name for all of its European operations however the U.S. business still operated under the Patricof & Co. name. By the mid-1990s Apax had become one of the larger private equity firms globally.

In 2001, Patricof & Co. adopted the Apax Partners branding and formalized its affiliation with its European business. In 2002, Apax Partners LLP was established.

In 2005, Apax announced it would acquire middle market leveraged buyout firm Saunders Karp & Megrue to augment its buyout business in the United States. In March 2006, Alan Patricof left Apax.