Gout, 18, had opted not to take part in this summer's Commonwealth Games in Glasgow and was instead focused on competing in the U20 Championships in Eugene, Oregon in August.
But after receiving the MRI report, Gout said the grade-three tear will keep him out of action for the remainder of the year, although he hopes to come back "better and faster and stronger" in 2027.
In April, Gout ran 19.67 seconds to set a world U20 record on his way to retaining the 200m title at the Australian Athletics Championships.
His time was quicker than sprinting great Usain Bolt's 19.93 at the same age in 2004.
Writing on Instagram,, external the teenager said: "I'm very disappointed but I have no other possibility but to accept the situation. I understand that this is part of athletics.
"My focus now will be on my rehab in the coming weeks and months and ensuring I come back in 2027 better and stronger and faster."
A grade-three tear is a complete rupture of the muscle or tendon, with the injury taking three to six months or longer to fully heal.
In a statement, Australian Athletics said Gout "has a long and exciting athletics career ahead of him".
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It added: "While this will be disappointing for Gout himself as well as his many fans, unfortunately injuries are part of the sport, and it is important that he takes the time to rehabilitate, recover and return to the track to compete when he is ready."
In June, Gout, who also claimed the U20 100m national title at the Australian Championships, made his senior Diamond League debut at the Bislett Games in Oslo.