Markstrom had 39 saves through regulation and overtime, and then stopped all three Tampa Bay attempts in the shootout to help the Panthers beat the Lightning 3-2.
Peter Mueller scored the only goal of the shootout, slipping a backhand shot past Tampa Bay goalie Mathieu Garon. The key was clearly Markstrom, who denied Teddy Purcell, Victor Hedman and Steven Stamkos in the tiebreaker.
"To me, (Markstrom) was the player of the game," Panthers coach Kevin Dineen said. "There were some quality opportunities and Markstrom stood tall when we needed him."
Florida needed its goalie early and often as the Lightning outshot the Panthers 41-25.
"He made some amazing saves tonight," Lightning forward Tom Pyatt said. "We had a lot of chances. Chances that were in tight -- Grade-A type chances -- but that's how it goes sometimes. Sometimes you get beat by a good goalie."
Markstrom's outstanding play was supported by an opportunistic Panthers offense, which converted on both of its power-play opportunities to take a 2-0 lead through two periods. Tomas Kopecky and Greg Rallo scored their goals off deflections of slap shots by T.J. Brennan.
Kopecky got his 13th score of the season at 8:36 of the first. Rallo got his first career goal as he deflected Brennan's shot from the point into the top corner of the net with 3:19 remaining in the second.
"Special teams did us in a little bit," Lightning coach Jon Cooper said. "We certainly outshot them and out-chanced them, but their goalie stood tall and they played `D' when they had to. That's it."
The Lightning finally made good on their numerous scoring chances in the third period. Tom Pyatt directed a pass from Teddy Purcell right above Markstrom's shoulder pad cut the Panthers' lead in half at 5:38.
Alex Killorn tied it just less than 5 minutes later when a slap shot from Victor Hedman bounced off the boards and found its way onto Killorn's stick, where he easily slipped it past Markstrom.
Markstrom, however, stopped Purcell and Martin St. Louis on point-blank shots later in the third period to send the game to overtime.
"It's a tough one," Pyatt added. "I thought we did a lot of good things out there and I thought we deserved better."
Rallo, a 31-year-old journeyman, has spent the majority of his 12-year career in the minor leagues. ... Brennan was originally credited with both of Florida's goals in regulations before they were changed. ... The Lightning made two trades Tuesday, sending defenseman Marc-Andre Bergeron to Carolina for forward Adam Hall and a 2013 seventh-round draft choice, and acquiring minor-league forward Philippe Paradis from the Blackhawks in exchange for defenseman Kirill Gotovets. ... The Panthers won their first game against the Lightning this season (1-2-1) and improved their road record to 6-11-1. ... The Lightning are now 2-0-1 since Cooper was named head coach.