Flags with Diagonals or Triangles

Most flags avoid the diagonal entirely, and for a mundane manufacturing reason: a band that runs straight across or straight up-and-down is trivially easy to cut and sew accurately from a bolt of cloth, while a diagonal has to be measured and angled correctly on every single copy or the flag looks lopsided. The handful of countries that used a diagonal anyway did so because the angle itself was carrying meaning that a straight band couldn't — usually motion, a sunrise, or a specific geographic split — which makes this one of the more genuinely purposeful shapes on this whole list rather than a decorative variation on a stripe.

The Democratic Republic of the Congo's flag is the clearest example of a diagonal chosen for its symbolism rather than its looks: a single yellow-fringed red band runs from the lower hoist to the upper fly across a blue field, adopted in its current form in 2006, with the diagonal explicitly read by the government as 'a radiant star lighting the country's future,' the sky-blue field for peace, the red for the blood of the nation's martyrs, and the yellow fringe for the country's mineral wealth. Namibia uses a nearly identical structural idea for a very different purpose: a red diagonal band edged in white splits a green upper-left field from a blue lower-right field at independence in 1990, deliberately dividing the flag into a green half for agriculture and vegetation and a blue half for the sky, ocean, and the Atlantic coastline's rainfall, with the sun placed directly on the diagonal itself.

Tanzania's diagonal tells a merger story rather than a landscape story. When Tanganyika and Zanzibar united in 1964, the new country needed a flag that visibly combined both predecessor states' symbolism, and the solution was a black diagonal band edged in yellow running corner to corner across a green-over-blue field — green for the mainland's agriculture, blue for the Indian Ocean and Zanzibar's maritime economy, and the black-yellow diagonal literally stitching the two halves of the design together the way the political union stitched the two territories together.

Brunei's flag uses two diagonal bands rather than one, and for reasons rooted in the country's specific 20th-century political history: a white and a black diagonal stripe cross the yellow field representing, per the Sultanate's own account, the country's two chief ministers, with yellow as the color of Brunei royalty since the 15th-century Bruneian Empire. The national coat of arms, added in the flag's center in 1959 when Brunei gained a written constitution, includes a crescent, a royal umbrella, and a banner with an Arabic inscription reading 'always in service with God's guidance,' making Brunei's diagonal one of the more layered designs in this feature despite its simple two-color-band appearance.

The Bahamas takes the diagonal in a completely different direction: a black equilateral triangle, point toward the hoist, sits against two horizontal aquamarine bands sandwiching a gold one, adopted at independence in 1973. The government's own explanation reads the black triangle as representing the vigor and force of a united people, with the triangle's point directed inward as if driving the nation forward — the only entry on this list where the geometric shape is a solid triangle rather than a diagonal band running the full width of the flag.

Two African flags use a triangle at the hoist in a structurally similar way to the Bahamas but for unrelated reasons. Eritrea's flag centers an olive wreath encircling an olive branch inside a red triangle pointing from the hoist, itself nested within a green triangle above and blue below — the red for the blood spilled in the 30-year war for independence from Ethiopia that ended in 1991, green for the country's agriculture, and blue for the Red Sea coastline the country fought to secure. South Sudan's flag places a blue triangle at the hoist bearing a single gold star over black-red-green horizontal bands separated by white fimbriations, with the triangle read as pointing toward the country's future and the star representing the unity of South Sudan's peoples at independence in 2011.

Jordan's triangle runs the opposite direction structurally: a red triangle, bearing a white seven-pointed star, extends from the hoist across black-white-green horizontal bands, adapted directly from the 1916 Arab Revolt flag. The seven points of the star, added when Jordan modified the Arab Revolt design after gaining independence in 1946, are explained by the government as representing the seven verses of the Quran's opening chapter, al-Fatiha — giving Jordan's triangle a religious layer that neither the Bahamas' nor Eritrea's version carries.

The Czech Republic inherited its blue triangle from a flag originally designed for the whole of Czechoslovakia in 1920, when the country needed to visually distinguish its flag from Poland's near-identical white-over-red bicolor; heraldic designer Jaroslav Kursa added a blue triangle at the hoist, drawing on the blue of the Moravian coat of arms, to break the visual tie. When Czechoslovakia split into the Czech Republic and Slovakia in 1993, the Czech Republic kept the flag unchanged despite a formal 1992 agreement that neither successor state would do so — a decision Slovakia at times objected to but never formally contested, leaving the Czech Republic flying a flag technically designed for a country that no longer exists.

Trinidad and Tobago's diagonal is the simplest story on this list and one of the most literal: a black diagonal band edged in white runs from the upper hoist to the lower fly across a red field, adopted at independence in 1962 with the designers stating plainly that the diagonal represents the meeting of fire (the sun, red field) and water (the sea, black band), and unity binding the nation's people together — no political merger, no war, no royal history, just an elemental metaphor rendered geometrically.

Seychelles pushes the diagonal idea further than any other flag by using five bands rather than one or two: blue, yellow, red, white, and green rays fan out diagonally from the lower hoist corner across the entire field, adopted in 1996 to replace an earlier vertical-and-horizontal design. The government describes the diagonal rays as radiating outward to represent a young nation moving into a dynamic future, with each color individually assigned a value — blue for sky and sea, yellow for the sun, red for the people's determination, white for social justice and harmony, and green for the land and natural environment — making Seychelles' flag the only one on this list to use the diagonal as a full radiating fan rather than a single band or triangle.

The Republic of the Congo, Tanzania's western neighbor across the Congo River and easily confused with the Democratic Republic of the Congo despite being a separate country, uses a diagonal green-yellow-red band running the opposite direction from DR Congo's, from the upper hoist to the lower fly, adopted in 1959 and readopted in 1991 after a period under a socialist-era flag. Because both Congos use a diagonal band in roughly the same three-to-four color families, distinguishing them at a glance depends on checking which corner the band originates from and whether a star sits inside it, a genuinely common point of confusion this site's flag identifier tool is built to resolve.

Because a diagonal or a triangle can carry a sunrise, a merger, a royal title, a war of independence, a radiating fan of national values, or a purely elemental metaphor depending on the flag, the groupings below separate the diagonal-band flags from the hoist-triangle flags, since those are two genuinely distinct geometric choices that happen to get lumped together in casual conversation about 'flags that aren't simple stripes.'