The decorated American, a seven-time gold medallist, will start one of the Olympic's most anticipated races on Saturday at La Defense Arena as the underdog based on times this year.
But the 27-year-old has long proved she can never be written off and was in a fighting mood when asked about her chances.
"I'm looking forward to the 400 free, day one. I like my chances," she said.
"I feel like I'm prepared and ready to race and that's all you can ask for."
Ledecky, who is the undisputed queen over 800m and 1500m, will have to raise her game to better Australia's Titmus in the shorter distance.
Titmus dethroned her in Tokyo three years ago, snatched her world record a year later and swam the second fastest time in history, 3min 55.44sec, last month.
Ledecky's best time this year is almost three seconds slower than the Australian, as is Canada's McIntosh, herself a former world record holder.
"They're great athletes and I've had the chance to race them quite a few times over the years now, especially Summer who has been training in the US," she said.
"It's always fun to race the best. We are the top three performers ever in that race, that just makes for a great field, a great race."
The trio are so dominant that they share the 27 fastest times in history with New Zealand's Erika Fairweather the only other current swimmer to breach four minutes.
Ledecky said Titmus and McIntosh drove her to keep improving.
"Those two have continued to raise the game, raise my game, and I know I have to bring my best," she said. "I think they know they also have to bring their best."
