The national flag of Poland (flaga Polski [ˈfla.ɡa ˈpɔl.ski]) consists of two horizontal stripes of equal width, the upper one white and the lower one red. The two colours are defined in the Polish constitution as the national colours. A variant of the flag with the national coat of arms in the middle of the white fess is legally reserved for official use abroad and at sea. A similar flag with the addition of a white eagle is used as the naval ensign of Poland.

White and red were officially adopted as national colours in 1831, although these were associated with Poland since the Middle Ages and were emphasized on royal banners. They are of heraldic origin and derive from the tinctures (colours) of the coats of arms of the two constituent nations of the Polish–Lithuanian Commonwealth (i.e., the White Eagle of Poland, and the Pursuer of the Grand Duchy of Lithuania, a white knight riding a white horse), both on a red shield.

Until 1831, Polish soldiers wore cockades of various colour combinations. The national flag was officially adopted in 1919. Since 2004, Polish Flag Day has been celebrated on 2 May.

The flag is flown continuously on the buildings of the highest national authorities, such as the parliament and the presidential palace. Other institutions and many Polish people fly the national flag on national holidays and other special occasions of national significance. Current Polish law does not restrict the use of the national flag without the coat of arms, as long as the flag is not disrespected.

Horizontal bicolours of white and red being a relatively widespread design, several flags are similar but unrelated to the Polish one. Two national flags (Indonesia and Monaco) have the red stripe above the white one. In Poland, many flags based on the national design also feature the national colours.

It is one of five flags that use the 5:8 ratio. The other four flags include those of Argentina, Guatemala, Palau, and Sweden.

The colours and flags of the Republic of Poland are described in two legal documents: the Constitution of the Republic of Poland of 1997 and the Coat of Arms, Colours and Anthem of the Republic of Poland and State Seals Act (Ustawa o godle, barwach i hymnie Rzeczypospolitej Polskiej oraz o pieczęciach państwowych) of 1980 with subsequent amendments (henceforth referred to as "the Coat of Arms Act").

Legislation concerning the national symbols is far from perfect. The Coat of Arms Act has been amended several times and refers extensively to executive ordinances, some of which have never been issued. Moreover, the Act contains errors, omissions and inconsistencies which make the law confusing, open to various interpretations and often not followed in practice.

Statutory coordinates of Polish national colours in the CIE xyY colour space with the tolerated colour differences in CIELUV

Colour		x	y	Y	ΔE
	White	0.315	0.320	82.0	4.0
	Red	0.570	0.305	16.0	8.0
Illuminant C, measurement geometry d/0

According to Chapter I, Article 28, paragraph 2 of the Constitution, the national colours of Poland are white and red. The Coat of Arms Act, Article 4, further specifies that the colours are white and red in two horizontal, parallel stripes of equal width, of which the top one is white and the bottom one is red. If the colours are displayed vertically, the white stripe is placed on the left from the onlooker's viewpoint. Attachment no. 2 to the Act shows the national colours in both horizontal and vertical alignment, as well as the official shades of both colours expressed as coordinates in the CIE xyY (CIE 1931) colour space with the tolerated colour differences (ΔE) specified in the CIE 1976 (L*, u*, v*) colour space (CIELUV).

The Constitution contains no mention of a national flag. Instead, the flag is defined by the Coat of Arms Act which specifies two variants of the national flag: the national flag of the Republic of Poland (flaga państwowa Rzeczypospolitej Polskiej) and the national flag with coat of arms of the Republic of Poland (flaga państwowa z godłem Rzeczypospolitej Polskiej). Both flags are defined in Article 6 of the act as follows:

1. The state flag of the Republic of Poland is a rectangular piece of cloth in the colours of the Republic of Poland hoisted on a flagpole.
2. The state flag of the Republic of Poland is also the flag specified in paragraph 1, with the coat of arms of the Republic of Poland placed in the middle of the white stripe.

The hoist to fly ratio for both flags is 5:8. For the latter flag, the proportion between the inescutcheon of the coat of arms and the hoist is 2:5. Images of both variations of the flag can be found in attachment no. 3 to the Coat of Arms Act.

Per Polish law, treating the national symbols, including the flag, "with reverence and respect" is the "right and obligation" of every Polish citizen and all state organs, institutions and organisations. Public disrespect, destruction or intentional removal of the flag is considered a crime punishable by a fine, penal servitude or up to one year of imprisonment. Official statistics show that crimes against national symbols are rare: 43 such crimes in 2003 and 96 in 2004 were less than 0.001% of all crimes registered in Poland in those years. Other, unspecified violation of regulations on the Polish flag is an infraction, punishable by a fine or up to one month imprisonment.

According to the Coat of Arms Act, everyone can use the Polish flag, especially during national and cultural events, as long as it is done in a respectful manner. This liberty in the use of national colours is a relative novelty. Until 2004, Polish citizens were only allowed to fly the Polish flag on national holidays. The use of both variants was restricted, but only flying the flag with coat of arms was, from 1955 to 1985, punishable by a fine or arrest for up to one year. After 1985, unauthorised use of any national symbol was an infraction. A possible explanation to such harsh measures was the fact that the officially promoted holiday of 1 May was separated by only one day from the pre-war (and current) national holiday of Poland, the anniversary of signing of the Constitution of 3 May 1791. While hoisting a flag on 1 May was acceptable, no later than the following day it had to be taken down.

That restriction and kind of state monopoly on the use of national symbols during the Communist regime made flying the Polish flag a symbol of resistance against the government. It became customary, as it still is, for workers to hoist Polish flags on plant buildings when going on strike. That is why the Polish flag, as a symbol of patriotism and resistance against the Communist rule, is part of the Solidarity trade union logo.

The following institutions are required by law to fly the national flag without coat of arms either on top or in front of their official buildings:

• the Sejm (lower house of parliament);
• the Senat (upper house of parliament);
• the President of the Republic;
• the Council of Ministers (cabinet) and the President of the Council of Ministers (Prime Minister);
• Voivodeship sejmiks (provincial legislatures);
• other state and local government organs.

Additionally, the national flag without coat of arms is used as an ensign for inland navigation.

While the ban on using the flag without coat of arms has been lifted, the use of the national flag with coat of arms is still legally restricted and should be flown only:

• on or in front of Polish embassies, consulates and other representative offices and missions abroad, as well as by Polish ambassadors and consuls on their residences and vehicles;
• at civilian airports and heliports (civil air ensign);
• on civilian airplanes – only during international flights;
• on buildings of seaport authorities;
• as a merchant (civil) ensign.

In practice, however, the restriction is often ignored and the two flags, with and without the coat of arms, are treated as interchangeable. The variant with the coat of arms, even though its incorrect usage, is often used by the Polonia, or Polish diaspora outside Poland, especially in the United States.

State and local government organs are legally required, and other institutions and organisations as well as all citizens are encouraged to fly the Polish flag on the following days:

• 1 May – State Holiday (May Day, formerly Labor Day);
• 2 May – Polish National Flag Day;
• 3 May – Constitution Day (along with Polish National Flag Day);
• 11 November – Independence Day.

The flag is often popularly flown during important sporting events, such as the FIFA World Cup, if Polish athletes are participating; and during an official visit of a particularly important person, especially a pope, in Poland. During a pope's visit, the national flag is usually flown together with yellow and white Church flags, and white and blue Marian flags. It is uncommon to fly the national flag on personal occasions, such as birthdays or weddings.

According to polls, about one out of three Poles say they own a Polish flag, and about one out of four fly it on national holidays. Such public display of patriotism is much more common in western Poland, especially in Greater Poland, than in other parts of the country.

Flags in Poland are used according to a customary, rather than legal, flag protocol. Apart from the obligation to treat the flag with due respect, Polish law does not offer a detailed code of correct usage of the Polish flag. Some organisations and public institutions, such as the Heraldic and Vexillological Institute and the Supreme Chamber of Control have proposed written flag protocols for the Polish flag, based on custom, flag protocols of other countries such as India and the United States, and common sense. These guidelines, however, are not legally binding.

Traditionally, the national flag is reserved to serve either informative or festive purposes. A single specimen of the flag on or in front of a public office building indicates its official role. Multiple flags, on the other hand, are normally used to decorate both public and private buildings to mark special occasions, such as national holidays.

In Polish heraldry, the tincture of the charge has priority in relation to the tincture of the field. In the case of Polish national colours, white, the colour of the White Eagle, should always be placed in a more honorable position than red, the colour of the field of the Polish coat of arms. In the most usual, horizontal alignment, this means that the white stripe is placed above the red one. If the alignment is vertical, the white stripe should be on the left from the onlooker's point of view. If the flag is hung vertically above a street, the white stripe should be placed on the left when looking in the direction of increasing house numbers. If it drapes a coffin, the white stripe should be placed over the heart.

The flag should be raised before 8 a.m. and lowered at sunset, and if flown at night, it should be illuminated. During a ceremonial raising of the flag, the national anthem is played so that the timing of the raising matches the duration of the anthem. Civilians pay respect by standing in a dignified manner; additionally, men uncover their heads. Members of uniformed services stand at attention; if their uniform includes headgear and they are not standing in an organised group, they also perform the two-finger salute. Colour guards dip their banners to the flag. (See video)

According to generally accepted standards of respect, the national flag should never be dipped to any person or thing. Care should be taken to prevent the flag from touching the ground, floor or water beneath it. It should be also secured from being torn off or falling to the ground and it should not be flown outdoors during a heavy rain, blizzard or very strong wind. The flag should never be flown dirty, torn or faded. When no longer in a fit condition to be used, it should be disposed of in a dignified manner, preferably by cutting it in half so as to separate the colours and then, burning.

When displayed with other flags, the Polish flag should be raised first and lowered last. Each flag must be flown from a separate pole of the same height, but the flag of Poland should be always placed in the most honorable position. It means that if the total number of flags is even, the Polish flag should be placed to its right of the other flags. If the total number of flags is odd, it should be placed in the middle. Alternatively, two Polish flags may be placed, one at each end of the row of flags. The order of precedence for flags is as follows:

• flag of Poland,
• national flags of other countries (in alphabetical order),
• voivodeship flags,
• county flags,
• commune flags,
• European flag,
• flags of domestic organisations,
• flags of international organisations,
• public services flags,
• corporate flags,
• other flags.

The President of the Republic may announce a period of national mourning. During that time Polish flags are flown at half-staff. If a flag is flown from a wooden pole rather than a staff or mast, a black ribbon is attached to the pole as a sign of mourning or a black flag is flown to its left from the national flag.

The earliest vexilloids (flag-like objects) used in Poland were known as stanice and probably resembled the Roman vexillum, that is a cloth draped vertically from a horizontal crosspiece attached to a wooden pole or spear. They served as both religious and military symbols as early as 10th century. With Poland's conversion to Christianity in 966, the stanice were probably Christianized by replacing pagan symbols with Christian ones. The royal banner of arms dates back to the reign of King Boleslaus the Generous (r. 1076–1079), but it was during the reign of King Ladislaus the Short (r. 1320–1333) that a red cloth emblazoned with the White Eagle of the arms of Poland was finally established as the Banner of the Kingdom of Poland, a symbol of royal authority used at coronations and in battles.

In the times of the Polish–Lithuanian Commonwealth (1569–1795), a banner of the Commonwealth was also used, combining the heraldic symbols of Poland and the Grand Duchy of Lithuania. The Commonwealth banner was initially plain white emblazoned with the arms of the Commonwealth which consisted of the heraldic charges of Poland (White Eagle) and Lithuania (Pursuer). Since both Polish and Lithuanian coats of arms consisted of white (Argent) charges in a red (Gules) field, these two colours started to be used for the entire banner. During the 17th century, the banner was usually divided into two, three or four horizontal, often swallow-tailed, stripes of red and white.

In the 18th and 19th centuries, European nations used cockades, or knots of coloured ribbons pinned to the hat, to denote the nationality of their military. In Poland, until 1831, there was no consensus as to what the colours of the national cockade should be. Polish soldiers wore white, white-and-red, blue-and-red or blue-white-red cockades.

The custom came to Poland from Saxony during the reign of Augustus II (r. 1697–1733), King of Poland and Elector of Saxony. During that time, the cockade worn by the Polish military had, like in Saxony, the form of a white silk ribbon with a knot in the middle. It was later replaced with a circular white cockade wrinkled toward the center, patterned after the cockade of the Kingdom of France. During the reign of King Stanislaus Augustus (r. 1764–1795), a white-and-red cockade came into use alongside the plain white one. In 1791, the Military Commission introduced a metal cross pattée as a more durable alternative to the cockade. However, many soldiers continued to either pin the cross to the cockade or wear the cockade without the cross. Polish military leaders and national heroes of the time, such as General Tadeusz Kościuszko and Prince Józef Poniatowski pinned plain white "national" cockades to their hats.