At the conclusion of the 2023-24 NHL season the league will be looking for a new uniform partner. It was announced today that Adidas and the NHL will end their partnership (seems like it was put in motion by Adidas) at the end of the 2024 Stanley Cup Finals.
Adidas took over the NHL contract after snagging it from Reebok, who at the time had been the partner with the NHL since 2004-05.
Prior to that teams used different companies for their jerseys. Some used CCM, some Nike, some Koho, etc, but having all of the teams under one manufacturer has been a thing for the league for almost 20 years now.