The flag of Amsterdam is the official flag

Flag

A flag is a piece of fabric with a distinctive design that is usually rectangular and used as a symbol, as a signaling device, or decoration. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another medium.The first flags were used to assist...

 for Amsterdam

Amsterdam

Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

, the capital city of the Netherlands

Netherlands

The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

. The current design of the flag depicts three Saint Andrew's Crosses

Saltire

A saltire, or Saint Andrew's Cross, is a heraldic symbol in the form of a diagonal cross or letter ex . Saint Andrew is said to have been martyred on such a cross....

 and is based on the escutcheon in the coat of arms of Amsterdam

Coat of arms of Amsterdam

The coat of arms of Amsterdam is the official symbol of the city of Amsterdam. It consists of a red shield and a black pale with three silver Saint Andrew's Crosses, the Imperial Crown of Austria, two golden lions, and the motto of Amsterdam. Several heraldic elements have their basis in the...

. The flag was adopted on February 5, 1975.

Meaning

The colors of the flag are derived primarily from the coat of arms of the city of Amsterdam, or rather from the shield in it. The meaning of the colors is unclear. According to the city government, its origin could go back the coat of arms of the Persijn family, which once owned a large tract of land in the capital.
In the coats of arms of two other Dutch cities, Dordrecht

Dordrecht

Dordrecht , colloquially Dordt, historically in English named Dort, is a city and municipality in the western Netherlands, located in the province of South Holland. It is the fourth largest city of the province, having a population of 118,601 in 2009...

 and Delft

Delft

Delft is a city and municipality in the province of South Holland , the Netherlands. It is located between Rotterdam and The Hague....

, the middle stripe symbolises water. In regards to Amsterdam, this black strip becomes the River Amstel

Amstel

The Amstel is a river in the Netherlands which runs through the city of Amsterdam. The river's name is derived from Aeme stelle, old Dutch for "area abounding with water"....

. These colors as well as the crosses are to be seen in the flags of both Ouder-Amstel

Ouder-Amstel

Ouder-Amstel is a municipality in the Netherlands, in the province of North Holland.-Population centres :The municipality of Ouder-Amstel consists of the following cities, towns, villages and/or districts: Duivendrecht, Ouderkerk aan de Amstel, Waver....

 und Amstelveen

Amstelveen

' is a suburban municipality in the Netherlands, in the province of North Holland. It is part of the metropolitan area of Amsterdam. The municipality of Amstelveen consists of the following villages and/or districts: Amstelveen, Bovenkerk, Westwijk, Bankras-Kostverloren, Groenelaan, Waardhuizen,...

.

Uses

AFC Ajax, an Amsterdam based football team who plays in the Dutch Eredivisie

Eredivisie

The Eredivisie is the highest football league in the Netherlands. The league was founded in 1956 two years after the start of professional football in the Netherlands. It is currently ranked the ninth best league in Europe by UEFA....

, uses the Amsterdam flag as their captain's armband.