Partners Group Holding AG is a Swiss-based global private equity firm with US$185 billion in assets under management in private equity, private infrastructure, private real estate and private debt.

The firm manages a broad range of funds, structured products and customised portfolios for an international clientele of institutional investors, private banks, individual investors and other financial institutions. The firm has completed more than 250 private equity investments in portfolio companies. In 2020, Partners Group became a constituent of the Swiss Market Index, an index of the 20 largest stocks in Switzerland. As of 2024,^[update] Partners Group is the fifth most-valuable publicly listed private markets firm in the world by market capitalisation.

Partners Group was co-founded in 1996 by Urs Wietlisbach, Marcel Erni and Alfred Gantner in Zug, Switzerland. Each of the co-founders contributed an equal share to the initial pool in the first year. In the firm's second year it had its first major milestone, launching a US$150 million small & midcap fund focused on investments in German-speaking Europe. The fund was a huge success in continental Europe. According to Institutional Investor magazine, this is partly due to the lack of competition at the time in Europe compared to North America. In the same article, co-founder Alfred Gantner stated you had to explain the term to people because private equity in the way we understand it today did not exist, it was called Risikokapital, risk capital, which was associated with venture capital.

In 1998, it completed a secondary transaction involving the private equity portfolio of Royal Dutch Shell's U.S. pension fund for US$265 million. At the time, it was the largest secondary transaction recorded. In 2002, Partners Group was an early investor in Esmertec, a Java client software maker. Partners Group is a joint stock company under Swiss law, listed on the Swiss Exchange since its 2006 initial public offering (minority floating). Around 45% of the shares are held by employees and partners. As of 2016,^[update] according to Forbes' annual billionaire's list, founders Gantner, Erni, and Wietlisbach are listed as three of the 25 wealthiest private equity managers in the world, each with net worths totaling $1.3 billion. Since 2001, Partners Group has pioneered evergreen funds in private markets and launched the first European Long Term Investment Fund (ELTIF) in 2017.

By 2005, Partners Group had $6 billion in assets under management, and was benefitting from the growing private equity industry. The Financial Times reported that private equity funds had raised $60 billion in first half of 2005 compared with $90 billion for the whole of 2004, demonstrating a growing demand for private equity. Wietlisbach was quoted stating he saw continued growth in the industry as "generalist funds will struggle to attract new money." Partners Group reported in its 2007 annual report that the firm had undergone a period of rapid expansion over the previous 24 months. During that time, it has more than doubled its assets under management, employee numbers and its annual net profit figure. As an early investor in Swiss-based semi-conductor manufacturer u-blox, Partners Group benefitted when the company announced it would be going public by the end of 2007.

On February 6, 2009, Partners Group announced that Peter Wuffli would be joining its board of directors. Wuffli had previously served as CEO UBS AG until 2007. Partners Group launched the Private Equity Master Fund in 2009. The fund was one of the first to meet the requirements of the Investment Company Act of 1940, and one of the first SEC-regulated funds available in the United States. Since its launch, the fund has consistently remained as largest entrant in this sector with US$16 billion in assets in 2024. According to the firm's 2010 Annual Report, total assets under management grew from €17.3 billion in 2009 to €21.4 billion in 2010.

Since 30 November 2011, Partners Group has been included in the MSCI Switzerland Index, after having been included in mid-September in the Swiss Small & Mid Cap Index (SMIM Index), which tracks the 30 biggest listed companies in Switzerland that are not listed by the Swiss Market Index.

At Private Equity International's 2012 awards, Partners Group were standout winners at the awards ceremony, as they were the only firm to win three categories. During the same year, Partners Group announced it was investing an undisclosed amount in solar panel production company, RioGlass. In July 2013, Partners Group announced the planned appointment of Christoph Rubeli and André Frei as co-CEOs, replacing Steffen Meister who had held the role since 2005. Meister would remain at Partners Group as a full-time executive member of its board of directors. In 2014, Partners Group announced that it had closed its third direct investment fund at its hard cap of €1.5 billion. Later that year, Partners Group and Duke Street Capital joined forces to acquire Voyage Care for £375 million, a specialist support company based in the UK. The Wall Street Journal reported the financial firm would likely continue its strategic focus on buyouts. It also held its first investor conference in the United States during the same year. Partners Group expanded its real estate portfolio in 2015 with a number of purchases in the United States and also in London. In London it acquired the 80 Fenchurch Street site next to Aldgate tube station, with plans to construct a 245,000sq ft office building in a joint venture with Marick Real Estate. This was after the firm brought the 0.6-acre site out of receivership earlier that year for over £50 million. In the US, hotels in New York and Tennessee were acquired, along with land in California. The United States real estate deals totalled US$163 million. In February 2016, Partners Group acquired Australia-based childcare firm Guardian Early Learning in a deal worth $440million.