A 30-year-old artist was fatally hit by a truck while riding her bike in Brooklyn Monday morning — the 18th cyclist killed on city streets this year.

Sunset Park resident Em Samolewicz was riding north on Third Avenue near 35th Street in her neighborhood just after 9 a.m. when a parked motorist opened the door of his van, forcing her to swerve into the road — where she was hit by a tractor-trailer, cops said.

The Massachusetts native — remembered by friends as a painter and yoga teacher — was rushed to NYU Langone Hospital–Brooklyn, but she could not be saved, authorities said.

The driver of the gray van admitted he didn’t check the roadway before opening the door.

“I’m supposed to look 100% to see if someone is coming,” said the man, who refused to give his name.

He said he’d just finished making an auto glass delivery, got back inside his vehicle on Third Avenue “and remembered I had to go out again.”

“I was trying to get out again,” the driver said. “The cyclist hit [the van door] and he or she lost control after I opened it. I closed it and opened it again.”

Mayor Bill de Blasio tweeted about the tragedy, noting: “It is AGAINST the law to open a car door into the path of a cyclist.”

The van driver was hit with a summons for opening his door unsafely in traffic, police said.

The truck driver, whose rig was marked with the Illinois-based company Gold Star Carriers, stayed at the scene and was also ticketed because his truck was too long.

Samolewicz’s former roommate, Sophy Naess, 37, remembered her as “a really kind and gentle person and also a great painter who will be missed.”

The pair were graduate teaching fellows together at Rutgers University three years ago, Naess said.

The owner of a Sunset Park art studio used by Samolewicz said she was “a decent person trying to make it here in New York.”

“She’s a kid, and to go out that way, it’s sad,” said the owner, who declined to give his name.

He added that she was a part-time yoga teacher. Third Root yoga studio in Flatbush lists Samolewicz as a staff member and says she was “interested in healing practices, variant histories, and poetics.”

Her death comes less than a week after two cyclists were fatally struck just hours apart in the city amid a spike in bike deaths.

According to NYPD stats, more people have been killed on bikes than riding motorcycles or driving cars this year.

Seventeen drivers and 13 motorcyclists have been killed so far this year, the NYPD said.

“The crash that claimed the life of a cyclist this morning — the eighteenth life lost in this manner on our streets in this year alone — is a horrific reminder of what is at stake in this street safety crisis facing our borough and our city,” Brooklyn Borough President Eric Adams said.

Adams said Third Avenue “is a particularly challenging corridor, as there is little infrastructure to accommodate cyclists, leaving them vulnerable.”

Additional reporting by Larry Celona