(277475) 2005 WK4, provisional designation 2005 WK4, is a stony, sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group that passed Earth within 8.2 lunar distances on 8 August 2013.

[7] It was discovered on 27 November 2005, by astronomers of the Siding Spring Survey at Siding Spring Observatory, Australia.

[2] In August 2013, 2005 WK4 was radar-imaged by the Deep Space Network dish at Goldstone Observatory, United States,[7] and had been observed previously at Arecibo Observatory in July 2012 (this was not a close approach though).

[8] 2005 WK4 measures approximately 250 meters in diameter, and has a rotation period of 2.595 hours.

[3][4][a] Its spectral type is that of an Sk-subtype, which transitions from the stony S-type to the uncommon K-type asteroids.