Former Dean of Research Linda Doyle defeated Prof Linda Hogan in the second round of voting.
Voting began this morning at 9:30am, with the final result expected to be announced around 1pm.
Eva Craig was elected president, with Rory Chinn elected vice president/treasurer.
Chuir Muireann Nic Corcaráin, Iar-Oifigeach na Gaeilge TCDSU agus an Leas-Uachtarán don Ghaeilge tofa don USI an rún chun cinn.
Prof Linda Doyle and Prof Jane Ohlmeyer both received 471 first-preference votes.
A rule introduced last month by the College led to the cancellation of laboratory practicals for most chemistry students.
The Gay Men’s Health Service is the only statutory sexual health service for gay men, bisexual men, men who have sex with men and transgender people in Ireland.
The union will lobby governments in the North and South of Ireland to ensure students are not 'financially, emotionally or socially disadvantaged' by mandatory hotel quarantine.
The motion was passed on the final day of USI’s annual meeting of its congress.
Clare Austick, the union’s current vice president for welfare, was elected president after running unopposed.