Donald Trump Jr. reported for jury duty Wednesday at Manhattan ​Supreme Court, where he snapped selfies with waiting prospective jurors, witnesses said.

The president’s eldest son fulfilled his civic duty at 100 Centre St. ​in Lower Manhattan ​and fiddled with his phone before being called in for a 2016 attempted robbery case before Justice Michael Obus.

During the hour-long lunch break, he took the stairs down 13 floors and headed for a bite at Forlini’s, a favorite courthouse haunt on nearby Baxter Street. He ordered the chicken parmigiana for lunch.

“He was pretty basic looking. He was called in with the other 80 people,” one juror told The Post. “The lady called his name twice and he was hesitant to say ‘here.’ You could hear it in his voice.”

​Wearing a gray sweater and khakis, ​Trump Jr. took photos with jurors and shook their hands in the jury room on the 15th floor, another juror said.

He also kept busy on Twitter, retweeting posts about his father, including one of a story saying Trump was more popular than Obama.

Trump Jr. was eventually sent two floors down to Obus’ courtroom, where he sat in the first row flanked by Secret Service with his arms stretched across the bench.

At times, he appeared bored, yawning and raking his hand through his hair as lawyers in the attempted robbery case began questioning prospective jurors for voir dire.

Members of Secret Service were waiting outside the courtroom as well as the courthouse.

“I think it’s hilarious he is serving. If I am here, he should be,” a juror said.