Williams was denied a 24th Grand Slam title of her career as she fell to a 6-2, 6-2 defeat.
Halep needed less than an hour on court to wrap up her second major tournament title, following success at the French Open last year.
The Romanian was like a wall in front of Williams as she showed Novak Djokovic-like defensive skills.
And Williams admitted there was nothing else she could have done differently.
“She literally played out of her mind, congratulations Simona,” Williams said.
“It was a little bit of a dear in the headlights for me.
“Whenever a player plays that amazing you have to take your hat off and give them a nod of the head.”
Williams is still one Grand Slam title behind Margaret Court’s all-time record.
But she vows to keep fighting in an attempt to strengthen her legacy.
“I have just got to keep fighting and enjoying the sport,” she added.
“I love coming here and playing in front of you guys, it has been really fun.
“My team is amazing. Thank you all for all the support and I love you all.”
More to follow