The win moves Federer past both Pete Sampras and William Renshaw, who each won seven titles at the grass-court major, for the most men's titles in the history of the event first held in 1877.
"I always believed that I could maybe come back and do it again. And if you believe, you can go really, really far in your life, and I did that," Federer said. "And I'm happy I kept on believing and dreaming, and here I am today for the eighth. It's fantastic."
When it ended, with an ace from Federer after merely 1 hour, 41 minutes of play, he raised both arms overhead. A minute or so later, he was sitting on the sideline, wiping tears from his eyes.
"Wimbledon was always my favorite tournament, will always be my favorite tournament. My heroes walked the grounds here and walked the courts here. Because of them, I think I became a better player too," said Federer. "To mark history here at Wimbledon really means a lot to me just because of all of that, really. It's that simple."
Truly, the outcome was only in doubt for about 20 minutes, the amount of time it took Federer to grab his first lead. Cilic, whose left foot was treated by a trainer before the third set started, was never able to summon the intimidating serves or crisp volleys that carried him to his lone Grand Slam title at the 2014 US Open. Cilic beat Federer in the semifinals during that run, his only win over the Swiss player.
Federer, 35, became the oldest champion at the All England Club, and he won his second Grand Slam of the year in impeccable fashion by not dropping a set throughout the two-week run. Federer joins Bjorn Borg (1976) as the only men in the Open era to win Wimbledon without losing a set, according to ESPN Stats & Information.
Federer last won the grass-court major in 2012, but he took the Australian Open title this year before skipping the French Open to focus on the remainder of the season.
That decision apparently paid off for the now-19-time Grand Slam champion.
With clouds overhead and a bit of chill in the air, the match's first game offered a glimpse at Cilic's apparent plan: Go after Federer's backhand. All five points Cilic won in that opening stanza came via mistakes by Federer on that stroke. Conversely, all three points won by Federer in that game were thanks to forehand miscues by Cilic.
Understandably, there were signs of nerves for both.
Federer's early play, in general, was symptomatic of jitters. For everything he has accomplished, for all the bright lights and big settings to which he's become accustomed, the guy whom many have labeled the greatest of all time admits to feeling heavy legs and jumbled thoughts at important on-court moments to this day.
And so it was that Federer, not Cilic, hit a double fault in each of his first two service games. And it was Federer, not Cilic, who faced the match's initial break point, 15 minutes in, trailing 2-1 and 30-40. But Cilic netted a return, beginning a run of 17 points in a row that Federer won on his serve. He didn't face another break point.
"I gave it my best," Cilic said. "That's all I could do."
It was as if the first indication of the slightest bit of trouble jolted Federer.
In the next game, Federer broke to lead 3-2 with the help of three errors by Cilic and one marvelous point. Cilic tried a drop shot; Federer got to it and replied at a tight angle. Cilic got that and offered a slick response of his own, but slipped and fell to the court, allowing Federer to flip a winner, eliciting roars from the crowd.
Federer broke again to take that set when Cilic double-faulted, walked to the changeover and slammed his racket on his sideline chair. Cilic then sat and covered his head with a white towel.
After Federer raced to a 3-0 lead in the second set, Cilic cried while he was visited by a doctor and trainer, and during a later medical timeout, his left foot was retaped by the trainer.
Cilic said in his postmatch news conference that he had a "really bad blister" that initially bothered him during his semifinal win. He said the pain prevented him from making quick movements during Sunday's match.
"Obviously was very tough emotionally because I know how much I went through [the] last few months in preparation with everything," Cilic said. "It was also tough because of my own team. They did so much for me. I just felt it was really bad luck."
Federer would break to a 4-3 edge in the third set, and all that remained to find out was how he'd finish. It was with his eighth ace, at 114 mph.
This caps a remarkable reboot for Federer, who departed Wimbledon a year ago with a lot of doubts. He had lost in the semifinals, yes, but more troublesome was that his body was letting him down for the first time in his career.
Earlier in 2016, he had surgery on his left knee then sat out the French Open because of a bad back, ending a record streak of participating in 65 consecutive Grand Slam tournaments. Then, after Wimbledon, he did not play at all the rest of the year, skipping the Rio Olympics, the US Open and everything else in an attempt to let his knee fully heal.
It worked. Did it ever.
"It's magical, really," Federer said. "I can't believe it yet."
The Associated Press contributed to this report.