The national flag of Belarus is an unequal red-green bicolour with a red-on-white ornament pattern placed at the hoist (staff) end. The current design was introduced in 2012 by the State Committee for Standardisation of the Republic of Belarus, and is adapted from a design approved in a May 1995 referendum. It is a modification of the 1951 flag used while the country was a republic of the Soviet Union. Changes made to the Soviet-era flag were the removal of communist symbols – the hammer and sickle and the red star – as well as the reversal of the colours in the ornament pattern. Since the 1995 referendum, several flags used by Belarusian government officials and agencies have been modelled on this national flag.

Historically, the white-red-white flag was used by the Belarusian People's Republic in 1918 before Belarus became a Soviet Republic, then by the Belarusian national movement in West Belarus followed by widespread unofficial use during the Nazi occupation of Belarus between 1942 and 1944, and again after it regained its independence in 1991 until the 1995 referendum. Opposition groups have continued to use this flag, though its display in Belarus has been restricted by the government of Belarus, which claims it is linked with Nazi collaboration due to its use by Belarusian collaborators during World War II. The white-red-white flag has been used in protests against the government, most recently the 2020–2021 Belarusian protests, and by the Belarusian diaspora.

The basic design of the national flag of Belarus was first described in Presidential Decree No. 214 of 7 June 1995. The flag is a rectangular cloth consisting of two horizontal stripes: a red upper stripe (which was inspired by the flag of the Soviet Union) covering two-thirds of the flag's height, and additional green lower stripe covering one-third. An additional vertical red-on-white traditional Belarusian decorative pattern, which occupies one-ninth of the flag's length, is placed against the flagstaff. The flag's ratio of width to length is 1:2. The flag does not differ significantly from the flag of the Byelorussian Soviet Socialist Republic (Byelorussian SSR), other than the removal of the hammer and sickle and the red star, as well as the reversal of red and white in the hoist pattern, from white-on-red to red-on-white. While there is no official interpretation for the colours of the flag, an explanation given by President Alexander Lukashenko is that red represents freedom and the sacrifice of the nation's forefathers, while green represents life.

In addition to the 1995 decree, "STB 911-2008: National Flag of the Republic of Belarus" was published by the State Committee for Standardisation of the Republic of Belarus in 2008. It gives the technical specifications of the national flag, such as the details of the colours and the ornament pattern. The red ornament design on the national flag was, until 2012, 1⁄12 the width of the flag, and 1⁄9 with the white margin. As of 2012, the red pattern has occupied the whole of the white margin (which stayed at 1⁄9).

The colours of the national flag are regulated in "STB 911-2008: National Flag of the Republic of Belarus" and are listed in the CIE Standard illuminant D65.

Standard Colour Sample of the National Flag

Colour	Colour coordinate		Y10
	x10	y10
Red	0.553 ± 0.010	0.318 ± 0.010	14.8 ± 1.0
Green	0.297 ± 0.010	0.481 ± 0.010	29.6 ± 1.0

2012–present	Green	Red
Pantone	355 C	1795 C
CMYK	93-0-100-0	0-96-82-1
HEX	#009739	#D22730
RGB	0-151-57	210-39-48

A decorative pattern, designed in 1917 by Matrona Markevich [be], is displayed on the hoist of the flag (as it was previously, on the 1951 flag). The pattern, derived from local plants and flowers, is a traditional type commonly used in Belarus. These patterns are sometimes used in woven garments, most importantly in the traditional ruchnik, a woven cloth used for ceremonial events such as religious services, weddings, and other more minor social functions, such as a host offering guests bread and salt served on a ručnik.

The husband of Matrona Markevich was arrested for anti-Soviet propaganda and executed during Soviet repression in Belarus in 1937, after which the family was dekulakised. The original ruchnik has not survived and was either confiscated by the NKVD in 1937 or destroyed during World War II. The brother of Matrona Markevich, Mikhail Katsar, head of the ethnography and folklore department at the Academy of Sciences of Belarus, was included into the commission that was ordered to create a new flag for the Belarusian SSR in 1951. A monument to Matrona Markevich was erected in Sianno in 2015.

Belarusian law requires that the flag be flown daily, weather permitting, from the following locations:

• The residence of the president of Belarus
• The buildings of the National Assembly of Belarus (House of Representatives and Council of the Republic)
• The building of the Council of Ministers of Belarus
• Courts of Belarus
• Offices of local executive and administrative bodies
• Above buildings in which sessions of local Councils of deputies take place (during the meetings)
• Military bases or military ships
• Belarusian embassies and consulates
• At checks points and posts at the borders of Belarus

The Belarusian flag is also officially flown on the sites of special occasions:

• Sessions of local executive and administrative bodies
• Voting/polling places
• Sports arenas during competitions (although the IOC has its own rules on flag display)

Belarusian diplomats and various government officials (such as the President and the Prime Minister) display the flag on vehicles. On special occasions, such as memorial services and family holidays, and it can be used at ceremonies and events hosted by public organisations, companies, and NGOs. The regulations were issued in the same decree that defined the Belarusian flag. The national flag has been incorporated into the badge of the guard units in the Belarusian armed forces. The pole should be three times longer than the width of the flag.

According to the 1995 presidential decree, the national flag is to be used on a staff that is coloured gold (ochre). Other parts of the protocol specify the finial (the metal ornament on a flag pole) as diamond-shaped and coloured in a yellow metal. In this diamond there is a five-pointed star (similar to that used in the national emblem). The diamond pattern represents another continuation of Soviet flag traditions. The Day of the National Emblem and Flag of Belarus is 15 May.

The white-red-white flag was used by the Belarusian People's Republic in 1918 before Belarus became a Soviet Republic, then by the Belarusian national movement in West Belarus followed by widespread unofficial use during the Nazi occupation of Belarus between 1942 and 1944, and again after it regained its independence in 1991 until the 1995 referendum.

Opposition groups have continued to use this flag, though its display in Belarus has been restricted by the government of Belarus, which claims it is linked with Nazi collaboration due to its use by Belarusian collaborators during World War II. The white-red-white flag has been used in protests against the government, most recently the 2020–2021 Belarusian protests, and by the Belarusian diaspora.

Before 1951, several different flags had been in use since the Revolution. The earliest flag was plain red, and was used in 1919 during the existence of the Lithuanian–Byelorussian Soviet Socialist Republic. After the formation of the Byelorussian SSR, the lettering ССРБ (SSRB) was added in gold to the top hoist. This design was established with the passage of the first Constitution of the Byelorussian SSR. It was later modified in the 1927 Constitution where the letters were changed to БССР (BSSR) but kept the overall design the same. This design was changed in 1937, when a hammer and sickle and red star were placed above the letters. The flag dimensions were also formally established as 1:2 for the first time. This flag remained in use until the adoption of the 1951 flag, which did away with the letters.

• 
  Lithuanian–Byelorussian SSR
  1919
• 
  Byelorussian SSR
  1919–1927
• 
  Byelorussian SSR
  1927–1937
• 
  Byelorussian SSR
  1937–1951

The flag of the Byelorussian SSR was adopted by decree on 25 December 1951. The flag was slightly modified in 1956 when construction details were added for the red star and the golden hammer and sickle. The final specifications of the flag was set in Article 120 of the Constitution of the Byelorussian SSR and are very similar to the current Belarusian flag. The flag had a length-to-width ratio of one to two (1:2), just like the flag of the Soviet Union (and the other fourteen union republics). The main portion of the flag was red (representing the Revolution), with the rest being green (representing the Belarusian forests). A pattern of white drawn on red decorated the hoist portion of the flag; this design is often used on Belarusian traditional costumes. In the upper corner of the flag, in the red portion, a gold hammer and sickle was added, with a red star outlined in gold above it. The hammer represented the worker, and the sickle the peasant; according to Soviet ideology, these two symbols crossed together symbolised co-operation between the two classes. The red star, a symbol commonly used by Communist parties, was said to stand either for the five social groups (workers, youth, peasants, military, and academics), the five known continents, or the five fingers of the worker's hand. The hammer, sickle and star were sometimes not displayed on the reverse of the flag. The purpose for this design was that the Byelorussian SSR, along with the Soviet Union and the Ukrainian SSR, were admitted to the United Nations in 1945 as founding members and needed distinct flags for each other. The designer of the flag was Mikhail Gusyev.