Garry Tan (Chinese: 陳嘉興; Pe̍h-ōe-jī: Tân Ka-heng; born 1967) is a Chinese-American investor who is the CEO of Y Combinator and a founder of Initialized Capital. He previously co-founded Posterous and Posthaven. He was an early employee at Palantir Technologies, and previously a partner at Y Combinator. Tan is also known for his engagement in San Francisco politics, both as a commenter on social media and as a political donor.

Tan was born in 1981 to a Chinese Singaporean father and a Burmese Chinese mother in Winnipeg, Canada. His father worked in a machine shop as a foreman, and his mother was a nursing assistant. The family settled in Fremont, California in 1991, and Tan graduated from American High School. He started programming at 14 and claims he found his first job by cold-calling the Yellow Pages.

He attended Stanford University from 1999 to 2003, and graduated with a bachelor's degree in computer systems engineering.

Tan worked at Microsoft and then became the tenth employee at Palantir Technologies. In 2008, Tan co-founded Posterous, a blogging platform, which was acquired by Twitter in 2012 for $20 million. He co-founded Posthaven after the shutdown of Posterous. He joined Y Combinator in 2011 as a designer in residence and partner. At Y Combinator, Tan helped compile a directory of "the best and the brightest interaction designers and visual designers" and wrote Coinbase's first seed round check in 2012. While at Y Combinator, Tan and fellow Y Combinator partners raised $7 million in venture capital funding to support Y Combinator alumni companies, including Instacart and Coinbase.

Tan was a founder of Initialized Capital, a venture capital fund. In 2012, Tan, Harj Taggar, and Alexis Ohanian operated Initialized Capital's $7 million first fund, followed by a $39 million second fund in 2013. In 2016, Initialized Capital raised a $115 million third fund. The latest fund was closed in December 2021 for $700 million. Through Initialized, Tan led investments in Instacart, Coinbase, and Flexport.

Tan has been listed on the Forbes Midas List from 2018–2022.

In August 2022, Y Combinator announced that Tan would become president of the company in January 2023, replacing Geoff Ralston. As president, Tan restructured Y Combinator’s investment operations by winding down its Continuity Fund and transferring follow-on investment decisions to group partners. He also initiated a consolidated fundraising effort with a stated goal of raising $2 billion across new funds.

Tan has been actively involved and influential in San Francisco politics, both by directing attention to various topics via his social media presence and through donations totaling to approximately $400,000 as of March 2024. Examples of causes espoused by Tan include increased funding for police to deal with property crime, opposition to regulation of self-driving cars, changes to education, decelerationism, Apple's monopoly on apps, and censorship by YouTube. Tan self identifies as a "moderate Democrat".