The flag of Croatia is one of the state symbols of Croatia. It consists of three equal size, horizontal stripes in colours red, white and blue. The flag combines the colours of the flags of the Kingdom of Croatia (red and white), the Kingdom of Slavonia (white and blue) and the Kingdom of Dalmatia (red and blue).
Those three kingdoms are the historic constituent states of the Croatian Kingdom. In the middle is the coat of arms of Croatia. The red-white-blue tricolour has been used as the Croatian flag since 1848. While the Banovina of Croatia existed within the Kingdom of Yugoslavia, it had a similar flag without the modern crown above the chequy. During the Independent State of Croatia, flag was like the modern, but without crown and there was letter "U" at the top left of the flag. Also, first field of Croatian chequy was white.
While Croatia was part of SFR Yugoslavia its tricolour was the same, but it had a five-pointed red star with a yellow border in place of the coat of arms. The star was replaced by the coat in May 1990, shortly after the first multiparty elections.
The current flag and the coat of arms were officially adopted on 21 December 1990, about ten months before the proclamation of independence from Yugoslavia and a day before the Constitution of Croatia on 22 December 1990. The shield is in the red and white checks of Croatia. Above is a crown made of shields of its various regions. From left to right they are the ancient arms of Croatia, Dubrovnik, Dalmatia, Istria, and Slavonia.source: wikipedia