Earl Grey Street was closed by police after the discovery at 3.15am on Monday, with officers still on the scene.
The man is said to have been found injured near the Bank of Scotland branch on the main road out of the city centre.
A Police Scotland spokesman said: “Inquiries into the cause of his injuries are ongoing. The road remains closed in the meantime while enquiries are being carried out.
“Police Scotland are appealing for any members of the public who were in the area at the time or who may have any information regarding the incident.”