John James Sykes (born 29 July 1959) is an English guitarist, best known as a member of Whitesnake, Thin Lizzy and Tygers of Pan Tang. He has also fronted the hard rock group Blue Murder and released several solo albums.

Following a stint in the heavy metal band Tygers of Pan Tang in the early 1980s, Sykes joined Irish hard rock group Thin Lizzy for their 1983 album Thunder and Lightning. He then joined Whitesnake, with whom he recorded the multi-platinum-selling self-titled 1987 album. However, Sykes was let go from the band before the record's release under acrimonious circumstances, which led to him forming his own group Blue Murder. After two albums and a live record, he embarked on a solo career. For the remainder of the 1990s and early 2000s, Sykes split his time between his solo career and a reformed Thin Lizzy, which he fronted until 2009, when he left to focus on his solo career.

Influenced by the likes of Jimmy Page, Ritchie Blackmore and Gary Moore, Sykes is known for his distinctive playing style, characterized by his fast alternate picking, use of pinch harmonics, and sense of melody. In 2004, he was included on Guitar World's list of "100 Greatest Heavy Metal Guitarists of All Time". In 2006, Gibson released a limited line of John Sykes Signature Les Pauls, which were modelled after his 1978 Gibson Les Paul Custom.