A former Stony Brook University professor on Tuesday pleaded guilty to siphoning off hundreds of thousands of dollars in grant money intended for cancer research and using the cash for his own personal expenses.

Geoffrey Girnun, 49, admitted in a Long Island federal court to stealing $78,000 in grant funding from the National Institutes of Health and $147,000 from the college, according to federal prosecutors.

Between 2013 to 2017, the feds say Girnun had the cash wired to two shell companies under his control that he falsely claimed were providing equipment for cancer-research projects.

Instead, he used the money as a personal piggy bank — paying off personal expenses like the mortgage payment for his house in Woodmere, LI, prosecutors say.

“With today’s guilty plea, Girnun has been held accountable for his unconscionable scheme to embezzle for his personal use hundreds of thousands of dollars in government funds that were intended to help find a cure for cancer,” US Attorney Richard Donoghue said in a news release.

Girnun officially resigned from Stony Brook last month. During his tenure there, he worked as the principal investigator on various research projects.

Girnun — who had initially been charged with wire fraud and money laundering — copped to a charge of theft of government funds and also agreed to cough up $225,000 in restitution.

He faces up to 10 years in prison when he returns to court for sentencing.