With one clutch shot at 9:32 of overtime, Alfredsson ended a decade's worth of frustration by sending the Senators to the Stanley Cup finals for the first time.
His goal sealed a 3-2 win over the top-seeded Buffalo Sabres on Saturday, allowing Ottawa to win the Eastern Conference finals in five games.
No one needed to remind Alfredsson that he was the only one to have played in Ottawa's 94 playoff games over 10 consecutive years; or that it took that long for the Senators to finally shed their reputation as postseason underachievers.
"It's kind of surreal right now," Alfredsson said. "We worked very hard for this, but you never take anything for granted. ... We respect Buffalo as a team. I think they've had a hell of a year. But I think they ran into us at the wrong time."
The Senators improved to an NHL best 12-3 this postseason and have yet to lose two games in any series after eliminating New Jersey and Pittsburgh in five games each in the first two rounds. Sweetest of all, perhaps, Ottawa had been eliminated by Buffalo in its previous three playoff meetings, including last year's second round.
"What else can you say about Alfie?" forward Jason Spezza said. "He's been our leader the whole time. It's only fitting he scores that winner."
It came on what began as an innocent-looking play, accepting Dany Heatley's pass on the fly and breaking into the Sabres zone on a 1-on-3 rush. Using Buffalo defenseman Brian Campbell as a screen, Alfredsson had his shot tip off the defender's stick and sneak just inside the right post.
Ottawa will now wait to face Anaheim or Detroit, and will start that series on the road. The Western final series is tied at 2, with Game 5 at Detroit on Sunday.
The Presidents' Trophy-winning Sabres were knocked out in the semifinals for the second straight year, after they significantly raised expectations in Buffalo.
"It's tough to swallow," Sabres co-captain Daniel Briere said. "I really believed it was our year. We just couldn't get it going."
Sabres goalie Ryan Miller stood at the bench afterward, shaking his head and rubbing his eyes
"It surprised the heck out of me," Miller said, referring to Alfredsson's goal. "He kind of hung me out. I didn't get a real good look and obviously, I came up missing it."
Another loser was the NHL, which lost its national U.S. over-the-air TV audience when NBC dropped its coverage of the game to show the Preakness Stakes just before overtime. The end of Ottawa's victory was broadcast instead on Versus, the league's main cable rightsholder that reaches far fewer homes than NBC.
The Sabres squandered a 1-0 lead in a game that was reminiscent of Game 2 of the series. Ottawa overcame a 2-0 deficit in that one and won 4-3 on Joe Corvo's goal in double-overtime.
Heatley and Spezza scored 3:40 apart to put the Senators up 2-1 with 39 seconds left in the second period Saturday.
The Sabres responded when Maxim Afinogenov wrapped in a rebound with 9 minutes left in regulation, just as Buffalo's two-man advantage ended.
The Senators, however, took over again and had the better chances down the stretch.
Antoine Vermette, on a short-handed breakaway, had Miller beat, but his shot hit the right post.
Miller then made a remarkable save 3 minutes into overtime, diving across and just getting the paddle of his stick on a shot by Spezza, set up by Alfredsson at the left post. Spezza was already raising his arms in celebration before realizing Miller made the save.
The Senators set a franchise playoff record by winning their fourth straight road game and improved to 7-1 overall.
"I don't think it's any secret that we're a good team," goalie Ray Emery said. "As a team, it was more of a pride thing. Last year, it was disappointing. It didn't feel right when we lost."
The Senators have been the superior team in the East long before the playoffs began. They overcame a 17-18-1 start and have gone 43-10-8 in their past 61 games, including playoffs.
"It feels great. I'm so happy for the guys," coach Bryan Murray said. "After the way we started the year, to do what they've done to get to this level. It's a very special group of people right now."
It was a special win for Murray. After becoming only the fifth coach to win 600 games earlier this season, Murray will coach in the Cup finals for the first time.
Jochen Hecht also scored for Buffalo and Briere had two assists.
Buffalo lost Game 7 of the East finals to eventual champion Carolina last year. This defeat was more disappointing considering the team returned mostly intact, proudly announced its Stanley Cup objective in September, and further raised expectations after leading the NHL with 53 wins and 308 goals.
The Sabres also face an uncertain summer with Briere and co-captain Chris Drury eligible to become unrestricted free agents.
Drury required 11 stitches after being struck on the chin by teammate Tim Connolly's point shot midway through the third period. Drury didn't return until 2 minutes into overtime. ... Sabres RW Dainius Zubrus didn't play because of a lower body injury, which limited him to 4 minutes in Game 4. Drew Stafford replaced Zubrus, returning after being a healthy scratch for 6 games. ... Senators RW Patrick Eaves returned after missing 11 games with a head injury.