Champions Series (senior men's tennis tour)

The Champions Series was a series of tennis tournaments designed for former champion members of the ATP Tour. It operated from 2006 to 2021.

It consisted of tournaments where top players of the sport competed in one-night, four-player events with two one-set semifinal matches and a one-set championship match played in one evening. Eligible players competing on the Champions Series either held a Top 5 singles ranking; been a Grand-Slam singles finalist, or a singles player on a championship Davis Cup team during their ATP tour playing careers. It also allowed one wild card of their choice at each event. The series was produced by Inside Out Sports & Entertainment. The minimum age to participate in a tournament was 30.

No matches were played in 2013 as the series realigned from the fall to the spring. A new match format was introduced to complete all play on a single evening, with only four players involved. The new format is two semi-final matches consisting of a best-of-one-tiebreak set, followed by a one-set final for the championship.