Masfjorden is a fjord in Masfjorden Municipality in Vestland county, Norway. The long fjord flows to the west and empties into the Austfjorden, the inner part of the Fensfjorden. It is separated from Austfjorden by a deep sill and has a maximum depth of .
The fjord is generally about wide. The innermost part of the fjord splits into two branches at the village of Solheim with the Matrefjorden going to the southeast to the village of Matre and the Haugsværfjorden going to the northeast to the village of Haugsvær. The village of Matre and the European route E39 highway sits at the innermost part of the fjord.
There are no bridges over the fjord, but there is one regular cable ferry route near the mouth of the fjord in the east. The ferry runs from the village of Masfjordnes in the south to Duesund in the north, a distance of just less than .