If a bunch of irate Venetians have their way, the star-studded dream wedding that Jeff Bezos, the Amazon founder, and his fiancée, Lauren Sánchez, are planning in the ancient city at the end of June could be a nightmare.

On Friday evening, representatives of various citizens groups gathered in a square near Rialto Bridge and vowed to organize a series of protests on June 26, 27 and 28, when hundreds of guests are expected to descend on the lagoon city for the lavish nuptials of Mr. Bezos and Ms. Sánchez, a journalist.

Though details of the festivities have been wrapped in secrecy, “we have our moles,” said Federica Toninello, a protest organizer, revealing that one of the venues could be the The Misericordia, a former charity turned events hall. “Bezos will never get to the Misericordia,” she vowed, urging the roughly 300 people present to take a stand. “We will line the streets with our bodies, block the canals with lifesavers, dinghies and our boats,” she said to loud applause.

She spoke under a large banner that read: “No Space [an image of a spaceship] For Bezos,” playing on his ownership of Blue Origin, the spaceflight venture. “We have to block Bezos, we have to block this idea of this city” as a tourist haven that has driven up housing costs so that most ordinary Venetians can no longer afford to live here, she said.

Representatives for Mr. Bezos and Ms. Sánchez did not respond to a request for comment.

Their wedding coincides with peak season in Venice, as tens of thousands of visitors arrive in the city daily, prompting City Hall to impose a controversial entry fee on weekends and holidays. Protesters said they were also concerned that the logistics of the wedding, including security for some top-tier guests, will further disrupt the life of Venice’s dwindling resident population.