Two cyclists are in the Royal Brisbane Hospital on Friday morning, following separate crashes in the inner city.

A man in his 40s suffered serious head injuries after crashing his bike into a rail on the Bicentennial Bikeway in the inner west just before 5am.

A cyclist has crashed under the Go Between Bridge, while minutes later another was in an accident at Newstead. Credit:File

A Queensland Ambulance Service spokesman said the crash happened under the Go Between Bridge.

The man was ventilated by paramedics on scene and transferred to the RBH in a serious condition.