An alligator is living in a lagoon in one of Chicago’s busiest city parks — and officials are working early Wednesday to remove the creature, police said.

The gator — estimated to be between 4 and 5 feet long — was first spotted at the Humboldt Park Lagoon on the city’s West Side early Tuesday by visitors who spotted the reptile’s head poking out of the water.

“During an early morning shoot, we encountered an alligator … YES!” photographer Rencie Horst-Ruiz posted on Facebook. “AN ALLIGATOR AT THE HUMBOLDT PARK LAGOON!”

Chicago police spokeswoman Kellie Bartoli said department officials confirmed later Tuesday while working with state reptile specialists that the animal was indeed in the lagoon and would be “humanely trapped” before being sent to a zoo to be evaluated.

Investigators have not determined how the gator got into the lagoon and the animal had not been trapped as of 7:30 a.m. Wednesday, Bartoli told The Post in an email. Exactly when the animal would be removed is unclear, she said.

Alligators are not indigenous to the state.

The unexpected sighting took on a life of its own on social media, spawning gator-themed hashtags and even an “HP Gator” Twitter account that had more than 70 followers as of Thursday morning.

Horst-Ruiz said she was initially in disbelief upon hearing a man say he spotted the animal as she readied for a Sweet Sixteen photoshoot in the park, she told Block Club Chicago.

“We thought no way,” she told the website. “We thought it would be a toy or something.”

Horst-Ruiz said the alligator was “close” to a pier at one point before returning to the middle of the lagoon, which is connected to a public beach currently closed due to high bacteria levels, Block Club Chicago reports.

Another witness said he “clearly” saw the gator with its eyes above the water and speculated that the animal had been ditched there by its previous owner.

“Why they would do that, I don’t know,” bystander Charlie Rizzo told the website. “Was it a sense of giving the animal freedom? Or just plain crazy? I don’t know what would motivate someone to do something like that.”

Bait traps have since been set up in the lagoon to capture the alligator, the Chicago Tribune reports.

It’s not the first time an alligator has been spotted near Chicago. A kayaker found an abandoned alligator last year near Waukegan, about 35 miles north of downtown Chicago, according to the newspaper.