The 21-year-old's time of 3:56.40 beat Ledecky's record by 0.06 seconds, a title the American has held for six-years.
"I'm just really happy," Titmus said after the race.
"I can't put myself up next to her. What she has done for female swimming has been insane: She's been at this level for 10 years"
"To be in the conversation with her, I feel completely honoured," she said.
"I hope now this is going to keep the battle going — give her some drive, hopefully, we can see how much faster we can keep going"
Titmus said she wasn't targeting the world record.
"I thought that if I went out there and did the best race I could with how I'm feeling, the world record was definitely within my reach," she said.
"Coming from a regional town out of Tassie, I feel like I can stamp that message that it doesn't matter who you are and where you come from, that you can achieve great things."
Titmus will not be competing at the World Championships in Budapest next month but will, instead, focus on preparing for the Commonwealth Games in Birmingham in July.
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