HD 17156 b, named Mulchatna by the IAU,[4] is an extrasolar planet approximately 255 light-years away in the constellation of Cassiopeia.

[5] The planet was discovered on April 14, 2007, by a team using the radial velocity method on the Keck and Subaru telescopes.

Careful radial velocity measurements have made it possible to detect the Rossiter–McLaughlin effect, the shifting in photospheric spectral lines caused by the planet occulting a part of the rotating stellar surface.

[7] This planet's spin-orbit angle was initially measured by Narita in 2007 as +62 ± 25 but has been remeasured by Cochran +9.4 ± 9.3 degrees.

[9] Due to its high eccentricity and large distance from its star, HD 17156 b has a low probability of ever entering a secondary eclipse.