A Massapequa man and his dog were killed in a head-on crash in Southold, police said Sunday.

The crash occurred at 11:25 a.m. Saturday on Main Bayview Road in Southold, police said.

Colin J. Ryan, 31, of Massapequa, was driving a 2009 Honda two-door sedan northbound when he “crossed over the solid double yellow lines” and struck a southbound SUV, said Southold Det. Edward Grathwohl.

The circumstances of the crash are being investigated, police said. When officers arrived at the scene, they found both vehicles in the roadway, “heavily damaged,” police said.

Ryan and the dog in his vehicle — described by cops as small and tan — were pronounced dead at the scene, police said.

Ryan’s family could not be reached for comment Sunday.

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The SUV driver, Antigone Amengual, 66, of Southold, was extricated from her vehicle — which took firefighters “over an hour,” according to Grathwohl.

Amengual was treated at the scene by the Southold Fire Department and then airlifted to Stony Brook University Hospital by Suffolk Police’s Aviation Bureau, police said.

She was listed in critical condition, said hospital spokeswoman Melissa Weir late Sunday afternoon.