15th World Science Fiction Convention
| Loncon I, the 15th World Science Fiction Convention | |
|---|---|
| Genre | Science fiction | 
| Dates | 6–9 September 1957 | 
| Venue | King's Court Hotel | 
| Location(s) | London | 
| Country | United Kingdom | 
| Attendance | 268 | 
The 15th World Science Fiction Convention (Worldcon), also known as Loncon I, was held on 6–9 September 1957 at the King's Court Hotel in London, United Kingdom. It was the first Worldcon held outside North America.
The chairman was Ted Carnell.