Madam or ma'am is a title for a woman. It is derived from the French madame, the equivalent of Mrs. or Ms., and literally signifying "my lady." The plural of madam in this sense is mesdames.

Madam is used in direct address, without the woman's name, for example when addressed by a stranger: May I help you, madam? In the United States, "Ma'am" (to rhyme with 'jam') is usually used. The male equivalent is sir.

In English-speaking countries, the wife of a foreign dignitary is called Madame (note final 'e') in direct address and formal correspondence (and not senora, frau etc.)

After addressing her as "Your Majesty," it is proper to address the Queen of the United Kingdom as "ma'am" (which should rhyme with "pam", not "palm") for the remainder of the conversation.

Madam is also used as the equivalent of Mr. in composed titles, such as Madam Justice, Madam Speaker, Madam President. Most of these titles are usually used only in direct address, without the woman's last name: one would say President Smith, not Madam President Smith, even if one would address her to her face as Madam President.

However, the title Madam Justice is used in third-person reference: Madam Justice Louise Arbour, Madam Justice Arbour.

In the United States Supreme Court, rather than adopting the title Madam Justice for female justices, the title Mr. Justice was replaced simply by Justice. Likewise, female presidents of the Republic of Ireland have preferred to be addressed simply as President in direct address, rather than Madam President. Female judges of the High Court of Justice of England and Wales are titled Mrs. Justice rather than Madam Justice.

Madam is also an informal term for a woman who runs a brothel or otherwise manages prostitution; a female pimp. The plural of madam in this sense is regular: madams.