Australian Open champion Naomi Osaka told Jennifer Brady she was "so sorry" on Sunday after making an embarrassing gaffe with the American player's name.

After beating Brady 6-4, 6-3 on Saturday to win her second Melbourne Park title, the ever-polite Osaka started her victory speech by asking if she preferred being called Jennifer or Jenny.

"Jenny," replied Brady.

Osaka then told the crowd: "Firstly, I want to congratulate Jennifer," which brought laughter from the 7,000-plus spectators on Rod Laver Arena.

Osaka apologised later on Twitter and said she was mortified at her blunder.

"Omg no (crying emoji)," the Japanese player wrote. "I promise you my mind thought I called her Jenny in that moment and I was so confused why the crowd was laughing. I'm so sorry."