Melvin, who turned 60 on Thursday, won three American League West titles in his 11 years as Oakland manager after previous stops as manager for the Seattle Mariners and Arizona Diamondbacks.
The Padres fired manager Jayce Tingler after stumbling to a 79-83 finish in 2021.
The Padres return the majority of their core, which includes infielder Jake Cronenworth, center fielder Trent Grisham, second baseman Adam Frazier and a strong starting rotation of Yu Darvish, Blake Snell and Joe Musgrove.
His tenure in Oakland was a wild success following tenures in Seattle and Arizona that ended with disappointment.
Melvin was not among the known candidates for the San Diego job, which included former New York Mets manager Luis Rojas and former Chicago White Sox manager Ozzie Guillen.
The acquisition of Melvin dovetails with their hopes of a quick recovery from a troublesome 2021 season, in which performance issues and clubhouse troubles torpedoed their hopes of winning the franchise’s first World Series.
San Diego’s ascent started with the signing of Machado and the star turn from Tatis, the 22-year-old who earlier this year signed a 14-year, $340 million contract.
Instead, a strong start to the season devolved into subpar performances and internal issues as the Padres tried to weather injuries to Tatis’ left shoulder, which he subluxed multiple times.
Oakland, in the meantime, is preparing for a transitional winter.