| Country | Flag description |
| South Georgia and the South Sandwich Islands | blue, with the flag of the UK in the upper hoist-side quadrant and the South Georgia and the South Sandwich Islands coat of arms centered on the outer half of the flag; the coat of arms features a shield with a golden lion centered; the shield is supported by a fur seal on the left and a penguin on the right; a reindeer appears above the shield, and below it on a scroll is the motto LEO TERRAM PROPRIAM PROTEGAT (Let the Lion Protect its Own Land) |
| Southern Ocean | void |
| Spain | three horizontal bands of red (top), yellow (double width), and red with the national coat of arms on the hoist side of the yellow band; the coat of arms includes the royal seal framed by the Pillars of Hercules, which are the two promontories (Gibraltar and Ceuta) on either side of the eastern end of the Strait of Gibraltar |
| Spratly Islands | void |
| Sri Lanka | yellow with two panels; the smaller hoist-side panel has two equal vertical bands of green (hoist side) and orange; the other panel is a large dark red rectangle with a yellow lion holding a sword, and there is a yellow bo leaf in each corner; the yellow field appears as a border around the entire flag and extends between the two panels |
| Sudan | three equal horizontal bands of red (top), white, and black with a green isosceles triangle based on the hoist side |
| Suriname | five horizontal bands of green (top, double width), white, red (quadruple width), white, and green (double width); there is a large, yellow, five-pointed star centered in the red band |
| Svalbard | the flag of Norway is used |
| Swaziland | three horizontal bands of blue (top), red (triple width), and blue; the red band is edged in yellow; centered in the red band is a large black and white shield covering two spears and a staff decorated with feather tassels, all placed horizontally |
| Sweden | blue with a golden yellow cross extending to the edges of the flag; the vertical part of the cross is shifted to the hoist side in the style of the Dannebrog (Danish flag) |
| Switzerland | red square with a bold, equilateral white cross in the center that does not extend to the edges of the flag |
| Syria | three equal horizontal bands of red (top), white, and black, colors associated with the Arab Liberation flag; two small, green, five-pointed stars in a horizontal line centered in the white band; former flag of the United Arab Republic where the two stars represented the constituent states of Syria and Egypt; similar to the flag of Yemen, which has a plain white band, Iraq, which has an Arabic inscription centered in the white band, and that of Egypt, which has a gold Eagle of Saladin centered in the white band; the current design dates to 1980 |
| Taiwan | red field with a dark blue rectangle in the upper hoist-side corner bearing a white sun with 12 triangular rays |
| Tajikistan | three horizontal stripes of red (top), a wider stripe of white, and green; a gold crown surmounted by seven gold, five-pointed stars is located in the center of the white stripe |
| Tanzania | divided diagonally by a yellow-edged black band from the lower hoist-side corner; the upper triangle (hoist side) is green and the lower triangle is blue |
| Thailand | five horizontal bands of red (top), white, blue (double width), white, and red |
| Timor-Leste | red, with a black isosceles triangle (based on the hoist side) superimposed on a slightly longer yellow arrowhead that extends to the center of the flag; a white star is in the center of the black triangle |
| Togo | five equal horizontal bands of green (top and bottom) alternating with yellow; a white five-pointed star on a red square is in the upper hoist-side corner; uses the popular pan-African colors of Ethiopia |
| Tokelau | the flag of New Zealand is used |
| Tonga | red with a bold red cross on a white rectangle in the upper hoist-side corner |
| Trinidad and Tobago | red with a white-edged black diagonal band from the upper hoist side to the lower fly side |
| Tunisia | red with a white disk in the center bearing a red crescent nearly encircling a red five-pointed star; the crescent and star are traditional symbols of Islam |
| Turkey | red with a vertical white crescent (the closed portion is toward the hoist side) and white five-pointed star centered just outside the crescent opening |
| Turkmenistan | green field with a vertical red stripe near the hoist side, containing five tribal guls (designs used in producing carpets) stacked above two crossed olive branches similar to the olive branches on the UN flag; a white crescent moon representing Islam with five white stars representing the regions or welayats of Turkmenistan appear in the upper corner of the field just to the fly side of the red stripe |