It’s the ultimate conspiracy theory — and New York City voters may get to vote on it come November.

A group funded by 9/11 conspiracy theorists has rounded up enough signatures to mount a ballot referendum questioning if 7 World Trade Center was really taken down as a result of the terror attack that fateful day.

The referendum would require the Buildings Department to investigate the collapse, even though two previous reports declared it had been caused by fires spread from the burning Twin Towers.

The measure is being pushed by the NYC Coalition for Accountability Now, which last Thursday presented more than 67,000 signatures to the City Clerk’s office — 37,000 more than required — to get the issue on the ballot.

“We are very concerned that a 47-story skyscraper that collapsed was not properly investigated,” said the group’s director, Ted Walter.

He wouldn’t say what he thought caused the collapse, but, when asked, said he doesn’t believe the government was involved.

The City Council will decide whether to add the issue to the ballot, assuming at least 30,000 signatures are declared legit.

But even if the council rejects the proposal by the Sept. 2 deadline, it could move forward if the group gets another 15,000 signatures by Sept. 4 — which 50 paid staffers are already out collecting in shifts.

The group’s Facebook page describes it as “a non-partisan organization comprised of 9/11 Family Members, First Responders, Survivors and concerned citizens committed to bringing about in [sic] independent, impartial investigation of the events surrounding September 11.”

Both the Federal Emergency Management Agency and the National Institute of Standards and Technology have investigated 7 WTC and determined it was brought down by fire.

“We still stand 100 percent behind the findings of our investigation into the collapse of 7 World Trade Center,” NIST spokesperson Michael Newman told The Post.

NYC CAN tried the same ballot stunt in 2009 but didn’t have enough signatures. This time around it has hired ballot professionals and raised nearly $200,000 from thousands of donors, including those who publicly question whether the government covered up the truth about 9/11.

NYC CAN has also quietly attempted to push its agenda with politicians, meeting with at least 10 current City Council members or their staff in recent years.

They include Brooklyn’s Jumaane Williams, chair of the Housing and Buildings committee and Daniel Dromm of Queens.

Even if the group gets enough registered New York City voters to sign on the dotted line on both rounds, it could still face a final legal challenge from the city.

Both the City Council and mayor’s office declined comment about the issue.