A 19th-century townhouse in the Turtle Bay neighborhood of Manhattan has been a perennial favorite shooting location with the producers of the hit television franchise “Law & Order” since 1994 — when the show was still in its early days.

And now that very residence, located at 333 E. 51st St., has hit the market for the first time in some 40 years for $6.9 million, The Post has learned.

The home has been owned by Joanne Reynolds, her husband Jim Reynolds, and daughter Gillian since 1982 — and was featured on both “Law & Order” and “Law & Order: Special Victims Unit” a total of four times.

“The ‘Law & Order’ producers were walking by the house randomly and knocked on the door to inquire about shooting,” Reynolds told The Post.

“They have shot four episodes at the townhouse — and it was featured as Judge Clarence Thomas’s house in one of them.”

Jim, a male model-turned-medical industry consultant, purchased the property for $675,000 at the time.

The Reynolds have decided for a change — with plans to move out to the West Coast.

The property was first featured on “Law & Order” on Nov. 23, 1994 on the episode “Virtue.” The home was later featured twice on “SVU” during season 5 in 2004 and season 8 in 2007, on the episodes “Poison” and “Responsible.”

The property last appeared on “Law & Order” this past March, in Season 22, on the episode titled “Bias.”

Occupying four stories and over 5,330 square feet, the dwelling features a living room with 16-foot-high ceilings and an original fireplace. An arched opening leads to the formal dining room.

Made up of four bedrooms and 3.5 bathrooms, there’s also a kitchen with floor-to-ceiling cabinetry, stone countertops and a built-in banquette in a windowed breakfast space.

A glass door opens to a winding staircase that leads to the 572-square-foot private garden.

The Asian-inspired primary bedroom features a recessed ceiling and custom wood panels. Level three includes a stately wood-paneled library.

“The producers love how each room is so unique from a visual standpoint — much like a TV/movie set — and they could shoot multiple scenes in all of the different spaces without changing location,” Reynolds added.

“I have maintained a friendly relationship with the producers and have their contact information. They pay $25,000 for one day of shooting so that’s a nice bonus.”

Mark David and Claudia Saez-Fromm with Corcoran hold the listing.