Capitol Hill is a densely populated residential district and a neighborhood in Seattle, Washington, United States. It is immediately east of Downtown Seattle and north of First Hill. The neighborhood is one of the city's most popular nightlife and entertainment districts and is home to a historic gay village and vibrant counterculture community.

In the early 1900s Capitol Hill was known as 'Broadway Hill' after the neighborhood's main thoroughfare. The origin of its current name is disputed. James A. Moore, the real estate developer who platted much of the area, reportedly gave it the name in the hope that the Washington State Capitol would move to Seattle from Olympia. Another story claims that Moore named it after the Capitol Hill neighborhood of Denver, Colorado, his wife's hometown. According to author Jacqueline Williams, both stories are likely true. The neighborhood was frequently referred to as Catholic Hill up until the 1980s due to its large Catholic population.

Capitol Hill is home to some of Seattle's wealthiest neighborhoods, including "Millionaire's Row" along 14th Avenue E. south of Volunteer Park (family residences on tree-lined streets) and the Harvard-Belmont Landmark District. The neighborhood is home to many distinguished apartment houses, including several by Fred Anhalt, as well as a few surviving Classical Revival complexes such as the Blackstone Apartments. The neighborhood's architecture did not fare so well in the post-World War II period; architect Victor Steinbrueck wrote in 1962 of the "tremendous growth of less-than-luxury apartments" that at first "appear to be consistent with the clean, direct approach associated with contemporary architecture" but whose "open outdoor corridors" totally defeat their "large 'view' windows" by giving occupants no privacy if they leave their blinds open to enjoy the view. He added, "most tenants close their blinds and look for another apartment when their lease runs out."

During the George Floyd protests of 2020, Cal Anderson Park and surrounding blocks along Pike and Pine Streets near the SPD East Precinct were occupied by protesters and declared the Capitol Hill Autonomous Zone (CHAZ).

Capitol Hill is situated on a steep hill just east of the city's downtown central business district. It is bounded by Interstate 5 (I-5) to the west (beyond which are Downtown, Cascade, and Eastlake); to the north by State Route 520 and Interlaken Park (beyond which are Portage Bay and Montlake); to the south by E. Pike and E. Madison Streets (beyond which are First Hill and the Central District); and to the east by 23rd and 24th Avenues E. (beyond which is Madison Valley).

Capitol Hill's main thoroughfare is Broadway, the commercial heart of the district. Other major streets in the area are 10th, 12th, 15th, and 19th Avenues, all running north–south, and E. Pine, E. Pike, E. John, E. Thomas, and E. Aloha Streets and E. Olive Way, running east–west. Of these streets, large portions of E. Pike Street, E. Pine Street, Broadway, 15th Avenue, and E. Olive Way are lined almost continuously with street-level retail. The Pike-Pine corridor (the area between Pike and Pine streets) from Boren Avenue through 15th Street is another main thoroughfare in Capitol Hill, full of coffee shops, bars, restaurants, and other food and music businesses. The neighborhood is largely characterized by mid-rise buildings occupied by an eclectic mix of businesses.

The highest point on Capitol Hill, at 444 feet (135 m) above sea level, is in Volunteer Park, adjacent to the water tower. Capitol Hill has several of Seattle's steepest street grades, including the steepest paved street at 21% on E. Roy Street between 25th and 26th Avenues E. (eastern slope).

The Link light rail system's Capitol Hill station is served by the 1 Line and opened in March 2016 as part of the University Link extension. The 1 Line connects the neighborhood to the University of Washington campus to the north, and Downtown Seattle to the south. The station is located along Broadway south of John Street and Olive Way.