Fitzsimmons was born the youngest child of two blind parents and was raised in Pittsburgh, Pennsylvania. He is said to have developed his multiple instrumental abilities from his mother and father, both of whom were recreational musicians. His childhood home even housed a fully functional pipe organ, hand-built by his father. He was taught the piano and trombone during elementary school, and began teaching himself guitar while in junior high school. He is also proficient at the banjo, melodica, ukulele, and mandolin, and is known for mixing folk music with electronica in some of his production. In addition to performance abilities, Fitzsimmons is credited as the engineer and producer of his first two releases. He is often compared to contemporaries Iron & Wine, Sufjan Stevens, and the late Elliott Smith.
Fitzsimmons' writing often includes reference to personal and family subject matter. His 2006 effort, "Goodnight," is said to have been based largely on his parents' divorce during his adolescence, and his 2008 work, "The Sparrow And The Crow," was written entirely about and following his own divorce. Fitzsimmons revealed on the syndicated music program eTown  that he recorded the work with a collaborator who he later learned was having a relationship with his wife while they were working on the recording. He revealed that this caused him to delay the release of this work.
A music video for the song "The Tide Pulls From The Moon" was released on February 8, 2011. In June 2011, Fitzsimmons toured in Europe, presenting his recent album "Gold In The Shadow," which was released March 22 via Nettwerk.
Fitzsimmons' album, "Lions," was released on February 18, 2014.
On May 12, 2015, Fitzsimmons released the first of a pair of mini-LP's concerning his family in Pittsburgh, titled "Pittsburgh.".
On April 1, 2016, Fitzsimmons released the second of the pair, his eighth album, entitled "Charleroi: Pittsburgh, Vol. 2". The album is about the grandmother he never knew - "Charleroi is the second half of the Pittsburgh story. The Pittsburgh album was about the grandmother I knew. Charleroi is about the one I never did.” per his website. Fitzsimmons embarked on a European tour to support his new album in April 2016, visiting 9 countries along the way.
On October 21, 2016, Fitzsimmons released his first live album, titled "William Fitzsimmons Live." The album showcases songs from across Fitzsimmons' career, recorded live at performances in Chicago, Amsterdam, and Paris. The record also features a cover of Fleetwood Mac's "Everywhere," recorded live in Cologne, Germany. Fitzsimmons released a video of his live cover of "Everywhere" on October 19, 2016. Abby Gundersen (sister of singer-songwriter Noah Gundersen, with whom Fitzsimmons toured in 2012) is featured on violin and vocals, and additional instrumentation is contributed by Jake Philips (acoustic guitar, electric guitar, banjo, and vocals) and Adam Popick (drums, synthesizer, rhodes, and acoustic guitar).
Fitzsimmons currently resides in Nashville, Tennessee.
iTunes US Best Singer/Songwriter Album 2008: The Sparrow and the Crow
iTunes Australia Best International Singer/Songwriter Album 2009: The Sparrow and the Crow
iTunes UK Best of 2009 Singer/Songwriter category: Goodnight
Beards NOW (Aust. publication) Honorable Mention in category 'Bushrangers Beards on non-Australians' 2010
The tour poster for the 2009 European tour designed by Stefan Guzy and Björn Wiede has been awarded for typographic excellence by the German Art Directors Club and was selected among the 100 best posters of 2009 in Germany.