The biggest wave of job actions in the history of America’s fast-food industry began at 6:30 a.m. on Thursday at a McDonald’s at Madison Avenue and 40th Street, with several dozen protesters chanting: “Hey, hey, what do you say? We demand fair pay.”

That demonstration kicked off a day of walkouts and rallies at dozens of Burger King, Taco Bell, Wendy’s, McDonald’s and other fast-food restaurants in New York City, organizers said. They said 14 of the 17 employees scheduled to work the morning shift at the McDonald’s on Madison Avenue did not — part of what they said were 200 fast-food workers who went on strike in the city.

Raymond Lopez, 21, an aspiring actor who has worked at the McDonald’s for two and a half years, showed up at the daybreak protest on his day off. “In this job, having a union would really be a dream come true,” said Mr. Lopez, who said his pay of $8.75 an hour left him feeling undercompensated. “It really is living in poverty.”

Workplace experts said it was by far the largest series of job actions at fast-food restaurants ever — part of an ambitious plan that seeks to unionize workers and increase wages at fast-food restaurants across the city.

The unionization drive, called Fast Food Forward, is sponsored by community and civil rights groups — including New York Communities for Change, United NY.org and the Black Institute — as well as the Service Employees International Union. The campaign has deployed 40 organizers since January to rally fast-food workers behind unionization, saying the goal is to raise wages to $15 an hour.

Rick Cisneros, the franchisee who operates the McDonald’s at 40th and Madison, said: “I value my employees. I welcome an open dialogue while always encouraging them to express any concerns or to provide feedback so I can continue to be an even better employer.”

Several mayoral candidates — including Christine C. Quinn, the City Council speaker; Bill de Blasio, the public advocate; John C. Liu, the comptroller; and William C. Thompson Jr., a former comptroller — were quick to voice support for the workers. As those candidates vie for the Democratic nomination, they are furiously jockeying for union support.

Mary Kay Henry, the service employees’ president, said the fast-food companies could easily afford to pay their employees more. “People who work for the richest corporations in America should be able to afford at least the basic necessities to support their families,” she said.

Labor leaders say they see an uptick in activism among low-wage workers — including last week’s Walmart protests — as workers grow increasingly frustrated about pay stagnating at $8 or $9 an hour, translating into $16,000 or $18,000 a year for a full-time worker.

Pamela Waldron, who has worked at the KFC in Pennsylvania Station for eight years, complained that she earned just $7.75 an hour and was assigned just 20 hours a week, meaning income of about $8,000 a year. She was picketing outside a Burger King on 34th Street, as several dozen workers and their supporters chanted, “How can we survive on seven twenty-five” — $7.25 an hour is the federal and New York State minimum wage.

“I’m protesting for better pay,” Ms. Waldron, 26, said. “I have two kids under 6, and I don’t earn enough to buy food for them.”

Miguel Piedra, a Burger King spokesman, said its restaurants provide entry-level jobs for millions of Americans, train and invest in workers, and “offer compensation and benefits that are consistent with the quick-service restaurant industry.”

Fast Food Forward said it had filed six complaints with the National Labor Relations Board, asserting that various restaurant managers had threatened to fire workers for striking or supporting a union or had improperly interrogated workers about backing the effort.

The protest on Thursday culminated in a rally with hundreds of fast-food workers and their supporters outside the McDonald’s on 42nd Street west of Times Square. They chanted, “Hey, hey, ho, ho, seven-twenty-five has got to go.”

Inside the McDonald’s on Madison Avenue on Thursday morning, a few workers made funny faces as their friends demonstrated outside. A few patrons, quaffing coffee and gobbling sausage McMuffins, eyeballed the protesters with concern through the restaurant windows.

Jocelyn Horner, 35, a graduate student, said she supported the protesters. “If anybody deserves to unionize, it’s fast-food workers,” she said.

A cashier whose name tag read “Milady” said she chose not to participate in the demonstration.

“At least I have a job,” she said.