Google co-founders Larry Page and Sergey Brin are stepping down from their roles within parent company Alphabet.
Page and Brin will remain directors of the firm, but have given up their CEO and president titles, respectively.
Sundar Pichai, who has been leading Google as CEO for more than four years, will stay in his role and also become CEO of Alphabet.
Alphabet, which also owns several other businesses, emerged in 2015 as part of a restructuring of Google.
Page and Brin, who started the search giant in 1998 in Silicon Valley, made the announcement in a Google blog post on Tuesday evening, saying the company has "evolved and matured" since it began.
"Today, in 2019, if the company was a person, it would be a young adult of 21 and it would be time to leave the roost," they said.
The pair added: "While it has been a tremendous privilege to be deeply involved in the day-to-day management of the company for so long, we believe it's time to assume the role of proud parents-offering advice and love, but not daily nagging!
"We are deeply committed to Google and Alphabet for the long term, and will remain actively involved as Board members, shareholders and co-founders. In addition, we plan to continue talking with Sundar [Pichai] regularly, especially on topics we're passionate about!"