While the Vikings did not provide the contract's value, ESPN reported the deal is worth about $96 million, with his contract going through the 2030 season.
O'Neill reported to the team's training camp on Tuesday as he is set to begin his ninth season in Minnesota.
Since being drafted 62nd overall in the 2018 NFL Draft, O'Neill has gone on to play 124 games for the Vikings, starting 120, starting 120 of them.
O'Neill, who will turn 31 in September, earned two Pro Bowl selections during his time in the league coming in 2021 and 2024. He also has three postseason starts to his name.