Williams was denied a 24th Grand Slam title in his career by falling in a 6-2, 6-2 loss.
Halep needed less than an hour on the court to conclude his second major tournament title, after success at the French Open last year.
The Romanian was like a wall against Williams when she showed Novak Djokovic's defensive skills.
And Williams admitted that there was nothing else he could have done differently.
"She literally went crazy, congratulations Simona," said Williams.
"He was a bit dear to me in the headlights."
"Every time a player plays that incredible, you have to take off your hat and wink at the head."
Williams remains a Grand Slam title behind Margaret Court's all-time record.
But she swears to keep fighting in an attempt to strengthen her legacy.
"I have to keep fighting and enjoying the sport," he added.
"I love coming here and playing in front of you, it's been a lot of fun."
"My team is amazing, thank you all for all the support and I love you all."
More to follow