Jason Murray Kubler (/ˈkuːblər/ KOOB-lər; born 19 May 1993) is an Australian professional tennis player. He has a career-high ATP singles ranking of world No. 63 achieved on 24 April 2023 and a best doubles ranking of No. 27 reached on 22 May 2023. His best career achievement was a major doubles title at the 2023 Australian Open, with compatriot Rinky Hijikata.

Despite a promising junior career, which included the junior world No. 1 ranking and comparisons to Rafael Nadal, Kubler has spent the majority of his professional career on the lower circuits due to a hereditary knee condition that results in weakened meniscus around the joints. The condition has plagued Kubler throughout his career, resulting in seven knee surgeries. Kubler also spent four years of his professional career playing exclusively on clay courts to avoid further structural damage to his knees.

Kubler was born in Brisbane, Australia to an Australian father and a Filipina mother. His father, John, introduced Kubler to tennis at the age of five, but died of cancer when Kubler was eight years of age. Kubler grew up in the north Brisbane suburb of Mango Hill with an older brother and a younger sister.

In 2009, Kubler became just the second player in history (after Rafael Nadal) to go undefeated through the World Youth Cup and Junior Davis Cup. Following his success at the Junior Davis Cup, Kubler won five titles in a row which saw his junior ranking rise to No. 3 in the world.

Kubler won six junior titles throughout his career and achieved the combined No.1 world ranking in May 2010 with a win–loss record of 67–17 in singles and 40–19 in doubles.

Kubler made his professional debut in September 2008 at the Australia F7 Futures event on the ITF Men's Circuit, the third tier for men's professional tennis. Kubler won through qualifying to make his main draw professional debut but lost in the first round to compatriot Marinko Matosevic.

In 2010, following continued success on the junior circuit, Kubler was granted wildcards into the Brisbane International and Sydney International qualifying draws, but failed to win a match at either event. He was then awarded a wildcard to make his ATP Tour and Grand Slam debut at the 2010 Australian Open. Drawn against 24th seed Ivan Ljubičić, Kubler was handily beaten 6–2 6–1 6–1 in a lacklustre display.

In April, Kubler won the first main draw professional match of his career at the Australia F3 Futures event in Ipswich, where he went on to make the final, losing to Brydan Klein. Kubler's best results for the remainder of 2010 were a string of semi-final appearances at Netherlands F2, Italy F23, Portugal F5 and Spain F37 Futures events. He finished the season ranked No. 535 in the world.