A Brisbane cyclist has died in hospital more than two weeks after suffering major head injuries in a collision on the southside.

The cyclist, aged 78, was rushed to hospital on September 4 after he collided with a black sedan at Moorooka.

The cyclist collided with a sedan at Muriel Avenue on-ramp to Ipswich Road. Credit:Google Maps

"Investigations indicate a collision occurred between a pushbike and a black sedan at the Muriel Avenue on-ramp to Ipswich Road just after 8am," a police statement read.

The 78-year-old man from Sunnybank Hills died at the Royal Brisbane and Women's Hospital on Wednesday after being rushed there with critical head injuries.

"Police are urging anyone who may have dash cam footage or who may have seen the accident to come forward," the statement read.

The forensic crash unit was investigating.