O'Neill, 19, made five appearances for Burnley in all competitions last season after joining from Brisbane Athletic.
The Australian then played 15 times on loan at Oldham, helping the Latics avoid relegation from League One.
"He will add things to our team that we need, he is athletic and well skilled," Fleetwood manager Uwe Rosler told the club website.
O'Neill joins strikers Conor McAleny and Jordy Hiwula, defenders Lewie Coyle and Harvey Rodgers and midfielder Kyle Dempsey in joining Fleetwood this summer.
He is the third Burnley player to be sent out on loan for the upcoming season, following Chris Long's move to Northampton Town and Alex Whitmore's switch to Bury.
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Fleetwood Town have signed teenage midfielder Aiden O'Neill on a season-long loan from Premier League Burnley.