Peaks Island is the most populous island in Casco Bay, Maine, and the second largest by land area among islands under the municipal jurisdiction of Portland. About three miles (4.8 km) from downtown, the island is served by Casco Bay Lines and has its own elementary school, library, and police station.

While small, the island has a variety of businesses, including an ice cream parlor, restaurant, grocery store, kayak rentals, golf cart rentals, art galleries, the Fifth Maine Regiment Museum, and the Umbrella Cover Museum.

At the time European explorers arrived on the Maine coast, the Wabanaki people foraged and hunted on Casco Bay islands in the warmer months including on Peaks Island.

Peaks Island was originally known as Pond Island. It became Michael's Island after Michael Mitton took a 60-year lease on the island in 1637 from his father-in-law George Cleeve. In 1661, Mitton's widow conveyed the island to a Boston merchant named John Phillips, and the island became known as Munjoy's Island for Phillips' son-in-law George Munjoy. In about 1670, the island became known as Palmer's Island for Munjoy's son-in-law John Palmer.

By 1670, Munjoy built a structure known as the Stone House that came under attack during a Wabanaki raid in 1675 during King Philip's War, with the family's fate unknown. The house was attacked again in 1676 after a group of mainland settlers taking refuge on nearby Cushing Island sought food on Peaks, and coming under attack attempted to defend themselves from the Stone House.

Warriors used Peaks Island in 1689 as a rendezvous point for an assault on Fort Loyal on Falmouth Neck, during King William's War.

By 1741, the island was known as Peaks Island, with the possibility the name stemmed from Joseph Peake, a soldier who may have lived on the island while serving in a militia company led by Capt. Dominicus Jordan.

At the time of the American Revolution, the island had three houses belonging to Thomas Brackett, Benjamin Trott Sr., and Col. John Waite Jr.