William Poromaa (born 23 December 2000) is a Swedish cross-country skier who competes internationally.

[1] He competed at the FIS Nordic World Ski Championships 2021 in Oberstdorf, where he placed fourth in the relay with the Swedish team.

[2] Poromaa is of Finnish descent through his paternal grandmother.

[3] All results are sourced from the International Ski Federation (FIS).

[1] a Distance reduced to 30 km due to weather conditions.