Isaka Aongor Čerňák-Okanya (born 9 April 1989) is an Australian professional football (soccer) player who last played for Thai Leagues T1 side Sisaket.
In his youth football playing days, Cernak played for the Peninsula Power, Westside FC, Brisbane City, QAS and the AIS football teams.
In 2008 Isaka Cernak joined A-League team Brisbane Roar (then called Queensland Roar), making 15 appearances and scoring a goal in his two seasons with the club. On 24 January 2009, Cernak made his senior debut as a substitute for Brisbane Roar against Perth Glory in a 4-2 win. In 2010, he left the Roar to join state rivals the North Queensland Fury.
In June 2010, Isaka signed a deal with North Queensland Fury to become their 15th signed player for their upcoming season. He made 14 appearances for the Fury, scoring one goal in his season with the Fury. Unfortunately for Cernak, the Fury were unable to extend his contract due to FFA ownership of the club.
During the 2010-11 season Melbourne Victory signed Cernak for the following season and Asian Champions League campaign as a replacement for departing striker Robbie Kruse to Bundesliga 2 club Fortuna Düsseldorf, with Fury unable to extend his contract due to FFA ownership of the club.
After being released by Melbourne during the January transfer window Cernak signed with Wellington Phoenix until the end of the season, having already agreeing to terms with Perth Glory for the following season.
Just a few months after signing with Wellington Phoenix, Cernak signed with Perth Glory.
In February 2014 Isaka signed for reigning A-League champions Central Coast Mariners. Isaka stated upon signing: “Being able to have one-and-a-half years to learn as a footballer off ‘Mossy’ (Phil Moss) and the players at Central Coast Mariners is really exciting for me.”
He joined SuperSport United in June 2015.
Cernak has represented Australia at U-20 and U-23 level. He has 19 caps and five goals at U-20 level and he currently has 7 caps and zero goals at U-23 level. He has won the Weifang Cup U-18 competition for Australia in 2007 and the International Cor Groenewegen Tournament at U-20 level in 2009.
Cernak was born in Brisbane, Queensland. His father is Ugandan, and his mother is Australian with a Scottish-Czech-American family background.