Emergency services were called to Luss at around 7.20pm on Sunday evening after receiving reports of a man in the water.
A 17-year-old was taken to Paisley’s Royal Alexandria Hospital in Paisley but later died.
A Police Scotland spokesman said: “At around 7.20pm on Sunday, police received a report of a 17-year-old man in the water at Loch Lomond just north of Luss.
“Emergency services attended and the man was taken to Royal Alexandria Hospital where he later died.
“A post-mortem examination will take place in due course however there are no suspicious circumstances surrounding the death.”
The tragic news comes days after a body was found in the search for a swimmer who went missing while in Loch Lomond.
A man in his mid 20s died after getting into difficulty while swimming with friends near the Maid of the Loch on Wednesday evening.