A mass brawl allegedly involving 20 people landed a man in hospital with a fractured skull and facial injuries.
The man was left with "life-changing" wounds after the fight in Teignmouth, police said.
Officers were called to Teign Street at about 00:50 GMT, where they were told by bystanders 20 people had been involved.
A 20-year-old man has been arrested on suspicion of assault and remains in custody.
Devon and Cornwall Police is appealing for witnesses.
Insp John Shuttleworth added: "We'd like to reassure the public that incidents of this nature, where someone is seriously injured, are reasonably rare.
"Sadly, alcohol can impact on the night-time economy in any area."