Gov. Martin O'Malley, Mayor Stephanie Rawlings-Blake and Baltimore County Executive Kevin Kamenetz will speak at a roughly hourlong celebration at the Inner Harbor Amphitheater at Light and Pratt streets that will start at 4 p.m.
Phelps, who became the most decorated Olympian of all time in London, his fourth and final Games, will speak as well. The Rodgers Forge native, who now lives in the city, won six medals in London, bringing his total to 22.
A big Ravens fan, Phelps will be introduced along with the football team as an honorary captain before the first game of the regular season, against the Cincinnati Bengals.
Among the athletes joining Phelps at the Inner Harbor will be 15-year-old Katie Ledecky of Bethesda, the youngest U.S. athlete to compete in London, whose stunning gold-medal win in the 800-meter freestyle broke the American record held by Janet Evans for 23 years and barely missed toppling the world record.
Other Olympians confirmed to attend are Suzanne Stettinius of Parkton, who competed in the modern pentathlon; windsurfer Farrah Hall of Annapolis; kayaker Scott Parsons of Bethesda; and rower David Banks, who is originally from Potomac but now lives in Berkeley, Calif.
O'Malley spokeswoman Raquel Guillory said the office is awaiting world from other athletes, including Allison Schmitt, a University of Georgia student who trained with Phelps at North Baltimore Aquatic Club and had a breakout Olympics, winning three gold medals, a silver and a bronze.
Schmitt joined Phelps last weekend in Las Vegas for a party at the Encore Beach Club, where bikini-clad waitresses presented him with a cake topped by the number 22 for his medals. They also hit Surrender nightclub, where Phelps joined Afrojack in the deejay booth.
Some Olympians have sent their regrets, including Georgia Gould, a bronze medalist in mountain biking who grew up in Guilford and Ruxton; Matthew Centrowitz, a runner who grew up in Arnold and now lives in Eugene, Ore., and just missed medaling in the 1,500-meter race; basketball players Carmelo Anthony and Angel McCoughtry, originally from Baltimore, and Kevin Durant, from Seat Pleasant; rhythmic gymnast Julie Zetlin of Bethesda; kayaker Caroline Queen of Darnestown; and cyclist Bobby Lea, who was born in Easton.
Guillory said the names of all of the Maryland Olympians as well as the Paralympians who are competing in London through Sunday will be read during the celebration.
She said she didn't think the celebration would add to what is expected to be increased traffic downtown for the Ravens game, which will be broadcast on "Monday Night Football."
"There will be people here anyway tailgating, so this gives them an opportunity to attend the event that afternoon as well," she said.
Guillory said she hoped the event would attract everyone from football fans to office workers.
"We just hope if Marylanders are in the area, they take the opportunity to stop by," she said. "It's going to be exciting."
At least one prominent fan will be there, applauding all the athletes, especially her son.
"It'll be the first time I've seen Michael since London," said his mother, Debbie Phelps, the former principal of Windsor Mill Middle School who now directs the Education Foundation, which enlists the business community in raising grant money for schools.
"It'll be exciting," she said of the celebration. "The people I have come in contact with, whether it's in New York at the train station or in Baltimore, they have such pride in what Olympians bring to this country."
If you go
Celebration of Maryland's 2012 Olympians and Paralympians
When: 4 p.m. Monday
Where: Inner Harbor Amphitheater