Alpha 441 was a planetoid located in the Badlands, where a Maquis munitions base was located.

Alpha 441 was the original target of the Cardassian missile Dreadnought, launched in 2370. The missile was able to reach the target, but then failed to explode due to an obsolete kinetic detonator used in the warhead. Afterward B'Elanna Torres reprogrammed the missile to destroy the Cardassian fuel depot on Aschelan V. (VOY: "Dreadnought")

This planetoid was only mentioned in dialogue.
According to Star Trek: Star Charts (p. 46) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Alpha 441 was located in the Alpha Quadrant. The planetoid was located on the outer rim of the Badlands.