The former One Direction star, 29, shared a poster of the pair facing off with the event set to take place at Old Trafford in Manchester.
The poster simply said: 'This Summer - announcement tomorrow,' while Liam captioned the post with an eyes emoji.
The singer did not offer any more details than that, with fans having to wait for further information to come on Thursday.
Fans were shocked by the poster, with many wondering if it was a late April Fool's Day or a 'wind up' by the pair
One fan wrote: 'April Fool's surely,' while Gogglebox star George Bragg agreed, saying: 'April Fool's was last week.'
Another demanded more informaton, writing: 'Liam James Payne please explain,' while a fourth said: 'Liam what is that?'
A fifth fan thought the pair might simply be making music together, saying: 'Have they recorded a song together?'