"Lonely Day" is the second single from the 2005 album Hypnotize by Armenian American rock band System of a Down. It was written by guitarist Daron Malakian, who also provides lead vocals on the track. The song received a nomination for Best Hard Rock Performance at the 49th Annual Grammy Awards.
"Lonely Day" features a dreary musical theme with a heavy chorus and a dual guitar solo near the end. The chorus is notable for featuring the double superlative "most loneliest". .