Nioghalvfjerdsfjorden is a fjord located in King Frederick VIII Land, in Northeast Greenland National Park of northeastern Greenland.

It is located at latitude 79° N (hence the name, which in Danish means "the fjord of seventy-nine") between Lambert Land and Hovgaard Island.

[1] The 79° North Glacier, also called Nioghalvfjerdsbræ, drains into this fjord.

The uninhabited Tobias Island is located 80 km east of the fjord.

In September 2020, satellite imagery showed that a big chunk of ice shattered into many small pieces from the last remaining ice shelf in Nioghalvfjerdsfjorden.