The Butterworth Building or Butterworth Block at 1921 First Avenue in Seattle, Washington was originally built as the Butterworth & Sons mortuary. The mortuary was moved to a larger location at 300 East Pine at Melrose in 1923. Located on a steep hill, the building has only three stories on the First Avenue side, but five on Post Alley. The building is listed on the National Register of Historic Places.

The building was the city's first purpose-built mortuary building. Jeannie Yandel in 2009 described it as "The city's first place for comprehensive death-related services from corpse retrieval to coffin sales." The building had the first elevator on the West Coast of the United States, used to transport bodies. A Seattle Mail and Herald account from August 1904, shortly after the building opened, calls it "without question of doubt, the most complete establishment of its kind in the United States…" A 2008 Seattle Times article describes the building, still extant, as "beautifully appointed in stained mahogany, art glass, ornamental plaster and specially designed brass and bronze hardware…" The basement, accessible through Post Alley at the rear, is now (as of 2009) home to Kells Irish Restaurant & Pub. Several recent accounts describe the Kells space as the former embalming room and crematorium, but the 1904 account says that the basement housed the building's heating plant, stables, and a storage space for funeral wagons.

The building is associated with several ghost stories. In 2010, the building was featured on an episode of Ghost Adventures and they found evidence that support theories of the building being haunted.