The green snake, believed to be “several feet long”, was seen by a passer-by in the undergrowth in Lingswood, reports the Daily Telegraph.
Police have advised that while it is not known to be a dangerous species, the beast should not be approached and witnesses should call 999 or the RSPCA.
It was last seen in a wooded area next to a large housing estate and has so far evaded capture.
A spokesman for Northamptonshire Police said: “Police were called at approximately 9.30am to a reported sighting of what is believed to be a large snake in the undergrowth.
“It is believed the snake may be a green Burmese Python.”
The Burmese python is the largest subspecies of the Indian python and one of the six largest snakes in the world, native to areas of Southern and Southeast Asia.
They can be found near water and in trees. Wild individuals grow to an average of 12ft long but can grow to 19ft in some cases.