Axel Vilfred Nielsen (13 December 1902 – 24 February 1970) was a Danish astronomer at the Ole Rømer Observatory in Aarhus from 1927 until his death in 1970.
In 1927 Nielsen was employed as an assistant with the Ole Rømer Observatory in Aarhus, later as head of section.
The Ole Rømer Observatory had been established in 1911; in 1956 it was handed over to the University of Aarhus.
Nielsen is a 10 km wide impact crater in the Oceanus Procellarum.
In 1944 he published a major work on the Danish astronomer Ole Rømer (1644–1710).