The 32-year-old native of Sweden has played in 770 games over the past 11 NHL seasons, all with the Vancouver Canucks. He is the Canucks' career leader in goals by a defenseman and was an All-Star during the 1998-99 season.
He received a seven-year deal worth $24.5 million.
Ohlund played in all 82 games last season, finishing with six goals and 25 points. He has 93 goals and 325 points during his career. In 52 playoff games, Ohlund notched nine goals and 28 points.
The Lightning not only feel they improved their roster immediately, but also are counting on Ohlund to be a mentor for Victor Hedman, the No. 2 overall pick in last week's NHL draft.