Sienna Rose Green (born 1 November 2004) is an Australian female water polo Olympian, who plays the centre back position.

[2][3][4] She competed for Australia at the 2024 Paris Olympics in the water polo women's tournament, and won a silver medal.

[5][6][10] She played in 2023 as a central defender for the University of California, Los Angeles, scoring 39 goals in the team's 29 games.

[6] She was captain and the highest goal-scorer of the Australian team at the 2022 FINA World Women's Youth Water Polo Championships in Belgrade, Serbia.

[7][17][18][19] She was the youngest Australian woman to compete in Water Polo in the Olympics, and scored three goals in seven games, six of which Australia won.