The win gave Wozniacki the first Grand Slam title of her career.
The No. 2 women's tennis player in the world beat No. 1 Halep 7-6, 3-6, 6-4 to claim the title. Wozniacki has 27 WTA titles and has been a fixture in the top 10 for a decade.
"I can still smile," Halep told reporters after the match. "I cried, but now I'm still smiling. It's just a tennis match in the end, but year, I'm really sad I couldn't win it. I was close again ...
"She was better, fresher and she had actually more energy in the end."
The match lasted two hours and 49 minutes. Wozniacki reclaimed the No. 1 ranking with the win.
"I'm sorry I'm just taking a second here to hug Daphne [the trophy]," Wozniacki said. "I've dreamt of this moment for so many years and to be here today is a dream come true. My voice is shaking and tonight is a very emotional moment."
"I also want to congratulate Simona. I know that today is a tough day. I'm sorry that I had to win today but I'm sure we'll have many matches in the future and it was an incredible match and incredible match. And again, I'm sorry."
Wozniacki's dad, agent and fiance, former NBA star David Lee, were in the stands for the match.
The men's final of the 2018 Australian Open pits Roger Federer against Marin Čilić at 2:30 a.m. EST Sunday at Rod Laver Arena in Melbourne.