Declan Sinnott (born 29 July 1950) is an Irish musician and record producer.
Originally from Wexford town, where his father was an optician and jeweller on Main Street, he came to Dublin in the late 1960s. Around 1970 he was a member of the poetry-and-music group Tara Telephone, in which he composed, sang, and played guitar. He and poet/percussionist Eamon Carr left Tara Telephone to form the Celtic Rock band Horslips, which Sinnott left in 1972, before the recording of Horslips' first album in 1973. He married Kathy Sinnott (née Kelly) when he was twenty two. They had nine children together, but are now separated. One of their children, Kevin Sinnott accidentally drowned while swimming at university in Georgia, US on September 21, 2009.
In the 1980s he was a member of Moving Hearts. He then devoted himself to production work with both Mary Black and her sister Frances Black. During a 13-year and six-album association, he toured all over the world with Mary Black. He has been working with Christy Moore for almost 30 years, since appearing on Christy Moore's Ride On album in 1984.