Harry Nielsen (born 3 May 1995) is an Australian cricketer, the son of former South Australian cricketer Tim Nielsen. During the 2017–18 season, he made his debut in all three major forms of the game, first-class, one-day and Twenty20 cricket playing for Cricket Australia XI in the JLT One-Day Cup and tour matches, the Adelaide Strikers in the Big Bash League and South Australia in the Sheffield Shield.
Nielsen started his career playing grade cricket for Woodville Cricket Club in Adelaide. He played his first against a higher quality opposition when he played for a Cricket Australia XI against the touring India national cricket team. Despite his team's poor performance, he scored 43 runs off 40 balls and was part of a 52-run partnership for the final wicket. His next major appearance was in another tour match, this time when South Africa were touring Australia, but instead of playing against the South Africans he played with them. When South Africa's wicket-keeper Quinton de Kock was unable to field and their reserve keeper had not yet arrived in the country, Nielsen had to leave partway through a grade cricket match for Woodville to stand in as their wicket-keeper. This gave him the opportunity to keep to a world-class bowling attack.
Nielsen started to play for South Australia in the Futures League. When he was the state's leading run-scorer in the competition for the 2016–17 season, he was upgraded to a senior contract with South Australia for the 2017–18 season.