Romarheimsfjorden is a fjord in Vestland county, Norway. The fjord flows through the municipalities of Modalen, Alver, and Osterøy. The western end of the fjord lies near the island of Hokøy where the fjord flows in to the Osterfjorden on its way out to sea. The fjord extends eastward from Hokøy for 11 kilometres (6.8 mi) along the border of Alver and Osterøy municipalities before entering Modalen where it continues to the Mostraumen, a 60-metre (200 ft) wide channel that is 650 metres (2,130 ft) long. On the other side of the channel, the fjord continues for another 18 kilometres (11 mi) where it is usually called the Mofjorden. That fjord ends at the village of Mo.

• List of Norwegian fjords