Surname law can refer to any law controlling the use of surnames. Specifically, it may refer to:
On 21 June 1934, Turkey adopted Surname Law which required all its citizens to adopt and use Western-style surnames.
The law in Japan requires a married couple to have a common surname. Most commonly it was the wife who took her husband's name. However, this law has been recently challenged on gender equality grounds. Japan is the only country in the G8 countries that has a formal law requiring a person to change their surname on marriage.