Sy is a given name, nickname/hypocorism (often of Seymour) and surname which may refer to:
Sydney () is the state capital of New South Wales and the most populous city in Australia and Oceania.
Systemic lupus erythematosus (SLE), also known simply as lupus, is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body.
Michael Sylvester Gardenzio Stallone (; Italian: [stalˈloːne]; born July 6, 1946) is an American actor, filmmaker, and screenwriter.
Synesthesia (also spelled synæsthesia or synaesthesia; from the Ancient Greek σύν syn, "together", and αἴσθησις aisthēsis, "sensation") is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway.
Roger Keith "Syd" Barrett (6 January 1946 – 7 July 2006) was an English musician, composer, singer-songwriter, and painter.
A synthesizer (often abbreviated as synth, also spelled synthesiser) is an electronic musical instrument that generates electric signals that are converted to sound through instrument amplifiers and loudspeakers or headphones.