[2] Özbilen, then competing as William Biwott Tanui, won the 1500 metres at the 2009 World Athletics Final in Thessaloniki, Greece.

[3] He holds the current world junior record in the mile run with his clocking of 3:49.29 minutes, achieved in Oslo on 3 July 2009.

[4] He was also part of the Kenyan team (with Gideon Gathimba, Geoffrey Kipkoech Rono and Augustine Kiprono Choge) that set a new world record of 14:36.23 in the rarely contested 4 x 1500 metres relay at the 2009 Memorial Van Damme Golden League meeting in Brussels, Belgium.

His surname was given him by his godfather and manager Önder Özbilen, who persuaded him in December 2010 in Kenya to immigrate to Turkey.

Özbilen also represented Turkey at the 2012 Summer Olympics in London, where he made the final of the 1500 meters, finishing 8th, with a time of 3:36.72.