Surname Sídnei (Sydney 
, Sídnei 
) , globally, is a common last name. The cognomen Sídnei is habitual in Saint Lucia, where it is quite a common surname, Trinidad and Tobago, and Mauritius, where it is quite a rare surname. In absolute terms, this name is the most popular in Nigeria, Australia, and the United States. More frequently, Sídnei is the forename as well as the last name.