Born in County Cork, Ireland, Tim O'Reilly moved to Hong Kong with his family when he was a baby.

[4] As a teenager, encouraged by his older brother Sean, O'Reilly became a follower of George Simon, a writer and adherent of the general semantics program.

[6][7] In 1973, O'Reilly enrolled at Harvard College to study classics and graduated cum laude with a Bachelor of Arts degree in 1975.

He started publishing computer manuals in 1983, setting up his business in a converted barn in Newton, Massachusetts, where about a dozen employees worked in a single open room.

As book sales decreased, O'Reilly laid off about seventy people, approximately a quarter of staff,[4] but thereafter rebuilt the company around ebook publishing and event production.

[11] O'Reilly serves on the board of directors of Safari Books Online, Maker Media, PeerJ, and the nonprofit organization Code for America.

O'Reilly first called an "executive conference" in 2004,[23] inviting five hundred technology and business leaders, followed by a public version of the event in 2005.

[3] He is considered the most enthusiastic promoter of algorithmic regulation,[28] the ongoing monitoring and modification of government policies via open data feedback.

[30] Originally proposed by Tim O’Reilly, and developed further in collaboration with Ilan Strauss and Mariana Mazzucato, “algorithmic attention rents” entails the use of a platform’s algorithms to allocate user attention to content which is more profitable or beneficial to the platform, at the expense of its ecosystem of users and third-party firms, content creators, website developers, etc.

[4] On 11 April 2015 O'Reilly married Jennifer Pahlka,[35][non-primary source needed][36] a former Deputy CTO of the US, and Founder and former Executive Director of Code for America.