The upturned hull of HMS Natal in Cromarty Firth, 1915. Image in public domain.
- The armoured cruiser HMS Natal is destroyed in Cromarty Firth, Scotland, following a series of internal explosions. The disaster occurs during Christmas celebrations when locals are invited aboard to view in a special film show. 421 crew and civilian men, women and children die. HMS Natal World War One Disaster Remembered
- Final planning for the evacuation of Helles continues, with all officers now informed of the plans. December 30
- French General Maurice Sarrail arrests the consular staff of the four Central Powers at Salonika and deports them from Greece, effectively assuming control of Salonika
- The P&O passenger ship Persia is torpedoed by a German submarine off the coast of Crete. She sinks in five minutes in one of the deepest parts of the Mediterranean, 343 of the 500 people aboard drown. Salvaging a Sense of History
