If the Niners win the Super Bowl this year, they might need to give Mike Posner a ring -- 'cause the singer-turned-breathing-instructor tells TMZ Sports he gave the team lung lessons before the season ... and it was so effective, it brought some of the SF players to tears.
The "I Took A Pill In Ibiza" artist has been all about the impact of oxygen on the body over the past couple years ... working with famed motivational speaker Wim Hof to become a certified breathing trainer.
Posner got so good at the techniques, the 49ers invited him out to give them a lesson just before they kicked off their year .