The Under-18 Series is a three-game series vs. Canada that features the U.S. Under-18 Women's Select Team. Twenty-five players are chosen to represent the U.S. following participation in the USA Hockey Women's National Festival.

The Series has been held annually since 2007.

The 2025 series took place at the Lake Placid Olympic Center in Lake Placid, N.Y., on August 13, 14 and 16. After dropping the first game of the series, Team USA went on to win game two and three, taking the series by a 2-0-0-1 (W-OTW-OTL-L) record, its first series win since 2017. 

Following the 2025 series, the U.S. and Canada have met 16 times, playing 48 all-time games, at the Under-18 Series and Team USA holds a 16-4-5-26 (W-OTW-OTL-L) record.