The Romanian thrashed the seven-time champion 6-2 6-2 in less than an hour on Centre Court, picking up a second Major crown to go with her French Open win at Roland Garros last year.
Halep was simply unstoppable, committing only three unforced errors — a record for a ladies' singles final — as 23-time grand slam champion Williams had no answer to her combination of energy and accuracy.
The day before the women's final, eight-time Wimbledon winner and Halep's idol Federer overcame Rafael Nadal in his semi-final, before offering his support to the world No.7, saying she should "back herself" and show a "winner mentality".
"I read what he said. I thank him. He is very nice," a smiling Halep said.
"His words made me happy. Also, I really believe that there is a chance if I listen to him. Because if you listen to him, you get the good things. So I did that."
The Duchess of Cambridge was in attendance in the Royal Box and afterwards spoke with Halep, who was thrilled with the introduction.
"It was an honour to play in front of her. I had the chance to meet her after the match. She's very kind, very nice," Halep added. "It was an extra boost when I saw all of them there, the Royal family. Winning in this position, it's really nice. It's unforgettable."
Halep, who was brought up on clay courts in her home country, conceded she doubted if Major success on grass would ever come her way.
"I never thought. I'm very honest. I never thought that I'm able to win on grass with all these players that are very tall and serving with a lot of power," she said.
"But this year, as I said every day, I started to feel the game more and more. I started to feel safe on court, which helped me a lot to believe.
"The French Open is better known because another two players [Ilie Nastase and Virginia Ruzici] won it from Romania. It's clay. We grow up on clay. We are more familiar to Roland Garros.
"But Wimbledon, I think it's very special for every country. Here the tennis was born, let's say. It's all the rules, a very prestigious tournament, makes it a little bit different and more special.
"Thinking that it is a possibility to win on grass, it was tough to believe because we don't even have a grass court in Romania.
"But I knew if we are patient and if we work hard, we get the feeling of the grass court. So I did this year and I did it pretty well."