Karunaratne, born in the coastal area of
Galle, received his primary and secondary education in
Dharmasoka College, Ambalangoda and
Royal College, Colombo, where he won the Royal Crown in 2001. He took up badminton at the age of 8, having been introduced to the sport by his father, who was a national level badminton player. He became the youngest ever Sri Lankan national badminton champion at the age of 16 in 2001 after winning his maiden national title on debut appearance at the Sri Lankan Badminton Nationals. At the
2014 Commonwealth Games, he was knocked out of the men's singles in the round of 16 by
Srikanth Kidambi. He was also part of the Sri Lankan mixed badminton team, which was knocked out at the quarterfinal stage by England. He won his first international badminton championship in 2011 after emerging victorious in the men's singles event at the
Puerto Rico International. He also set a record for winning most consecutive number of men's singles title at the Sri Lankan Badminton Nationals during 9 occasions from 2000 to 2009. In 2012, the Sri Lankan
Daily News called him "Sri Lanka’s undisputed badminton champion". He was selected to captain the
Sri Lankan contingent to the
2012 Summer Olympics in his debut Olympic appearance and was also the flagbearer for Sri Lanka during the
closing ceremony of the 2012 Summer Olympics. On 30 July 2012, Karunaratne defeated world eighth-ranked
Kenichi Tago of Japan 2–0. Karunaratne defeated Tago 21–18, 21–16 in 44 minutes at the
Wembley Arena in the Olympic men's badminton singles Group C at the
2012 Summer Olympics. The
Associated Press quoted him as saying: "This is the biggest win in the history of Sri Lanka badminton".
India's
Parupalli Kashyap defeated him in a closely fought pre-quarter match. Niluka Karunaratne signing autographs for fans (London 2012 Olympics).jpg|Karunaratne signing autographs for fans Niluka Karunaratne (London 2012 Olympics).jpg|Karunaratne at the London 2012 Olympics He made his second Summer Olympics appearance at the
2016 Summer Olympics representing Sri Lanka amid various difficulties as he was not eligible to compete in local and international badminton events due to the temporary ban on Sri Lankan Badminton Federation imposed by the
Badminton World Federation in 2015. In January 2021, he tested positive for
COVID-19 along with his younger brother Chamika and Niluka was disbanded from the National Badminton Association. However, he pledged to participate in badminton competitions after recovering from COVID-19 and in February 2021, he along with his younger brother and national cricketer Chamika Karunaratne played in the first round encounters in the men's singles of the Sri Lankan Badminton Nationals 2020. He announced his retirement from competing in local events after claiming the national badminton title for the record seventeenth time in 2021. However, he continued to compete in foreign competition with the aim of qualifying for the
2020 Summer Olympics in
Tokyo. In May 2021, Niluka reached the semifinals of the 56th edition of the Portuguese International Badminton Championships but was eliminated from the semis after losing to Germany's
Max Weisskirchen. He also qualified to represent
Sri Lanka at the 2020 Summer Olympics after receiving tripartite commission quota from Badminton World Federation and it would also mark his third appearance at the Olympics and also went onto become the sixth Sri Lankan competitor to qualify for the Tokyo Olympics. He will also become the first Sri Lankan badminton player to compete at three successive Olympics. He announced that he would officially retire from international badminton after competing at the delayed 2020 Tokyo Olympics in July 2021. He also holds a position in the banking sector as a bank employee. == Controversies ==