The 34-year-old Australian joins Luke Killeen as a confirmed starter for Spires next year, after a successful 2024 season.
Tungate won his second Australian Championship in January and scored a total of 202 points from 21 appearances for Spires.
He was then named Spires rider of the year by Oxford Speedway fans at last week’s end-of-season party.
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Tungate said: “It was an easy decision to return to Oxford in 2025, after a good year riding for the club this season. It’s the most enjoyable time I’ve had riding in England.
“A big thank you to everyone involved in the Oxford Speedway club and I can’t wait for next season.”
Oxford team manager Peter Schroeck added: “We’re delighted to have Rohan back with the Spires again in 2025.
“He did a very good job for us in 2024. We didn’t have to chase him much to come to Oxford, he really wanted to return to British Speedway and he’s as keen to ride for us again next season.
“There will be a few changes for Rohan next season, such as his Polish team moving into the top league over there.
“He’s a quality rider, and that the fans voted for him as rider of the year for the Spires shows that he is popular with them too.”