1RXS1609 b is an extrasolar planet orbiting around the star 1RXS1609. It is approximately 470 light years from Earth.

It is a gas giant, which is larger then Jupiter, at about 14 Jupiter masses. The planet is notable for its extreme distance from the star - approximately 330 AU, or 50 billion kilometres / 31 billion miles. This presented some serious challenges for the current models of planetary formation: the timescale to form a planet by core accretion at this distance from the star would be longer than the age of the system itself. One possibility is that the planet may have formed closer to the star and migrated outwards as a result of interactions with the disk or with other planets in the system. An alternative is that the planet formed in situ via the disk instability mechanism, where the disk fragments because of gravitational instability, though this would require an unusually massive protoplanetary disk.