Doctor Who Series 8 starts on BBC1 on Saturday 23 August 2014. This is the first series of the 12th Doctor.
Doctor Who Series 8 also starts on the same date on BBCAmerica.
The first episode is called Deep Breath.
The last episode we saw the 12th Doctor was at the end of the christmas special 'Time of the Doctor' where the 11th Doctor regenerates into the 12th Doctor.