The unnamed woman, believed to be in her 20s, was crossing the intersection at Douglas and Humboldt streets at the time.
The tour bus was travelling down Humboldt Street and hit the woman while turning left onto Douglas Street.
Victoria Police said the tour bus driver is being interviewed by investigators.
"It looks like [the woman] was crossing on a walk signal, that's what the witness accounts state, so she had the right of way," said spokesman Mike Russell.
Police investigations are continuing at the scene and traffic is being temporarily rerouted.