NGC 3642 is a spiral galaxy in the constellation Ursa Major. The galaxy has a low-ionization nuclear emission-line region. It is located at a distance of circa 30 million light years from Earth, which, given its apparent dimensions, means that NGC 3642 is about 50,000 light years across. The galaxy is characterised by an outer pseudoring, which was probably formed after the accretion of a gas rich dwarf galaxy.
The nearby spiral galaxy PGC 34666 is located about 150 million light years away with a visual magnitude of approximately +15. The galaxies PGC 2585851 and PGC 2586019, located about 1 billion (10^9) lightyears away, are also visible. Several of the other PGC-galaxies lies about 800 million lightyears away.