Stamkos, who had missed his last three games with a lower-body injury, was cleared from the score sheet.
The Lightning was 3-1 ahead when the Capitals finally fought back in the third. Jakub Vrana closed the gap and Alex Ovechkin tied the score with his 17e goal of the season, on the power play.
The Russian striker has not only forced an overtime, but has also joined Teamu Selanne as the third most productive scorer in the history of the National Hockey League (NHL) in numerical superiority with this 255e success.
Evgeny Kuznetsov also took advantage of the power play earlier in the game to outsmart Andrei Vasilevskiy, who faced a total of 35 shots.
At the other end of the ice Braden Holtby gave in to Brayden Point, Mikhail Sergachev and Alex Killorn. He made 27 saves in the match.