Harry Visinoni, who plays Seb Franklin in the TV soap, went to brush his teeth on Saturday when he saw the reptile "staring at him" in his home in Hale.
It is thought the snake had slithered off from its previous owner and into a wall cavity, said the RSPCA.
The charity has named it Lulu, which it said seemed "appropriate".
After seeing the reptile curled up in his bathroom, Mr Visinoni ran out and called for his girlfriend Ellie Isaac.
Opening the door briefly, the couple "watched as the snake then slithered on to the top of the toilet and sat on the seat just staring at us".
After discussing what they should do, they returned but found the python had disappeared.
The pair then spent a "sleepless" night "dreaming about snakes", before calling the RSPCA in the morning.
Animal rescue officer Sonia Hulme arrived and eventually located the snake behind the bathroom radiator.
'On the throne'
According to the RSPCA, the royal python is a fairly docile species but can bite when threatened.
And although the animal was "quite feisty", she managed to catch it using a pillowcase.
"I thought it was quite apt that this royal python was found on the throne - and as she is a female we thought it would be appropriate to call her Lulu."
Ms Hulme said it was likely Lulu had escaped from her previous owner and lived in the wall cavity of the flat.
Snakes can often survive with long gaps between meals, she added.
Lulu is now in the care of a specialist reptile keeper at the RSPCA and is in "good condition".
Actor Harry Visinoni has starred in Coronation Street since October 2016 as builder Seb, the son of mechanic Abi Franklin.