Firefighters battling a fire at a Darwin home were stunned to discover a four-metre crocodile living in the backyard.

Emergency services were alerted to the blaze after a neighbour saw smoke pouring from the first floor windows of the Fannie Bay house yesterday.

Upon arrival, firefighters discovered the first floor had been completely engulfed, and the blaze had started to creep into the lower floor of the Horitos residence.

“I would say the flames were a good metre out the window, you could feel the heat from the other side of the street,” one neighbour told 9NEWS.

Firefighters managed to extinguish the inferno within 10 minutes, however the building was irreparably damaged.

They were then notified that one resident had yet to evacuate: a four-metre pet crocodile by the name of “Albert”.

Albert, who inhabits a water-filled pen in the property’s backyard, has been with the Horitos family for over three generations, spanning a period of more than 50 years.

The crocodile was not affected by the fire, however with his owner’s home destroyed, his future appears uncertain.

Rangers are yet to determine whether Albert will remain on the property or be relocated.

NT Parks and Wildlife spokesman Tom Nichols said it was the first time he’d witnessed a crocodile living in such a fashion in the middle of Darwin suburbia.