It’s an outrage of Super proportions!

Old-school comics artist Al Plastino got the shock of his life at New York Comic Con recently, when he learned a nearby exhibitor was about to auction his own most valuable “masterpiece” — the original drawings for “Superman’s Mission for President Kennedy,” from a commemorative edition printed soon after the assassination.

For 50 years, Plastino, 91, believed his long-gone bosses at DC Comics had made good on their promise to donate the iconic ten pages of art to the John F. Kennedy Memorial Library, at Harvard.

But the library says it never received the artwork. And now, it’s in the hands of the Dallas-based Heritage Auctions, where it was due to be gaveled off at starting bid of $200,000 on the assassination’s 50th anniversary — until bad publicity halted the sale, at least for now.

“I almost started crying,” Plastino told The Post of seeing his beloved artwork, which he called “my pride and joy,” in the hands of a nearby exhibitor.

“The guy tells me, ‘We got your work,’ and I said, ‘What? How the hell did you get it?’ He wouldn’t tell me where he got it.”

“I was thinking about my grandchildren,” the elderly artist added. “When I pass on, I want them to be able to see it — of course!”

Heritage, in turn, says that for the past two decades, the pages have been in the hands of the same anonymous private collector, who bought them at a Sotheby’s auction for $5,000 in 1993, and now wants to sell them.

“We have no reason to believe our consignor does not have the right to sell the piece, and nobody has shown us any evidence that he doesn’t,” said senior consignment director Steve Borock.

But advocates for comic book artists say that since the art was never given to the museum, Plastino remains the rightful owner. Comic book publishers, they claim, only buy the publishing rights to an artist’s work, not the work itself. Publishers generally dispute this, and it’s an issue that’s been debated for decades.

“He never gave up ownership of the art because DC never purchased it from him or paid sales tax,” asserted Kris Adams Stone, daughter of comic book legend Neal Adams. She added that legal papers are being prepared to halt the auction for good.

The sale, originally slated for Nov. 21, 22 and 23 to take advantage of the 50th Anniversary of the Kennedy assassination, has now delayed indefinitely, a spokesman told The Post late Friday.

“He’s devastated,” Plastino’s daughter, MaryAnn Plastino Charles, 55, told The Post.

“He is 91, he has prostate cancer, and this is not helping him at all,” she said of her dad, who lives on Long Island,

“He started drawing Superman when he was 17 years old,” added the daughter, who manages her dad’s business affairs. “Every time he talked about what he had done in the past, he would mention this project. Many, many times he has spoken about how proud he was of this art.”

Plastino had drawn “Superman’s Mission for President Kennedy” in collaboration DC Comics writers and editors and the Kennedy administration, as a promotion for the president’s national physical fitness program.

The issue was slotted for the end of November, 1963 — but was quickly shelved when Kennedy was assassinated. Weeks later, the Johnson administration asked that the original be published, which DC Comics did, first adding a commemorative title page showing a spectral JFK looming benevolently over the capital.

“This story, prepared in close cooperation with the late President Kennedy, was scheduled for publication in Superman No. 168, when word of his tragic assassination reached us,” the title text reads.

“We immediately took it off the press and substituted other material. However, White House officials have since informed us that President Johnson wanted it published, as a tribute to his great predecessor. And so, we dedicate to the memory of our late, beloved president this plea for his physical fitness program, to which he was wholeheartedly devoted to during his life.”