The accident happened just 8.15 pm near Baroda Street just above the Ormeau Embankment.
The Belfast Health Trust said the man was in a critical condition in the intensive care unit at the Royal Victoria Hospital.
The Ormeau Road was closed following the collision but has since reopened.
The PSNI’s Collision Investigation Unit and investigators from Translink are probing the crash.
The accident is not far from where a cyclist was killed several years ago by a lorry. The driver of the lorry was later charged with death by dangerous driving but that charge was later withdrawn by the prosecution
A white bike has been attached to railings near the accident scene in his memory.