LOS ANGELES — Wikipedia, the online encyclopedia, has been plunged into controversy after one of its most prolific contributors and editors, a professor with degrees in theology and canon law, was exposed as a 24-year-old college dropout.

The editor, who called himself Essjay, was recruited by staff at Wikipedia to work on the site’s arbitration committee, a team of expert administrators charged with vetting content on the “free encyclopedia that anyone can edit.”

But no one apparently vetted the credentials of Essjay, who claimed to be a professor of religion at a private university and contributed to an estimated 20,000 Wikipedia entries.

Essjay was Ryan Jordan, a 24-year-old from Kentucky with no advanced degrees who used texts such as “Catholicism for Dummies” to help him correct articles on the penitential rite or transubstantiation.

He was unmasked after the New Yorker magazine referred to Essjay’s contributions to the site and how he would spend up to 14 hours a day editing, “correcting errors, and removing obscenities.”

The piece described him as a “professor of religion with a Ph.D. in theology and a degree in canon law” and noted he was serving his “second term as chair of the mediation committee,” which rules on disputes over information posted on the site.

But last week, Essjay was forced to resign after a critic of the online encyclopedia told the New Yorker his biographical information was fake.

“He holds no advanced degrees,” the magazine stated. “At the time of publication, neither we nor Wikipedia knew Essjay’s real name.”

Essjay had told them he hid his identity because “he feared retribution from those he had ruled against online.”

In a statement on Wikipedia, Jimmy Wales, the Web site’s cofounder, said he had asked Essjay to “resign immediately.”