The 21-year-old's ban included any finals the Cats played.
The punishment followed an alleged incident involving a woman.
The AFL commended the Cats for their strong stance.
"With this sanction, the Geelong Football Club and its leadership group have sent a powerful message to the AFL industry and the community more broadly that violence against women is never acceptable," AFL football operations manager Adrian Anderson said.
"The AFL's respect and responsibility policy is very clear that inappropriate player behaviour will not be tolerated and Geelong deserves to be commended for its unequivocal stand."
Along with his AFL ban, Stringer will have to sit out the next four VFL rounds and be made to attend behavioural education programs.
"The club is committed to two major outcomes from this situation," Geelong said in a statement.
"Firstly, to reinforce the AFL's respect and responsibility policy to all players and members of the club.
"Secondly the club will support Stringer and encourage him to learn from this experience and to continue to commit himself to develop as a person and a player."
Geelong did not detail what the "unacceptable" behaviour involved.
The club's penalty was recommended by the player leadership group, with input from officials including general manager of football Neil Balme and coach Chris Scott.
Stringer has been questioned by police, who are still investigating last Friday's incident, although no charges have been laid.
Stringer has spent the past two years on the Cats' rookie list, but was unable to play during 2010 because of a hip injury and was restricted by a knee injury last season.
The midfielder was elevated from the rookie list to make his AFL debut in round four this season and has played every game since.