23rd World Science Fiction Convention
| Loncon II, the 23rd World Science Fiction Convention | |
|---|---|
| Genre | Science fiction | 
| Dates | 27–30 August 1965 | 
| Venue | Mount Royal Hotel | 
| Location(s) | London | 
| Country | United Kingdom | 
| Attendance | ~350 | 
| Filing status | Non-profit | 
The 23rd World Science Fiction Convention (Worldcon), also known as Loncon II, was held on 27–30 August 1965 at the Mount Royal Hotel in London, United Kingdom. It was the second Worldcon to be held in London, following the original Loncon in 1957.
The chairman was Ella Parker.