| Country | Flag description |
| Saint Barthelemy | the flag of France is used |
| Saint Helena | blue with the flag of the UK in the upper hoist-side quadrant and the Saint Helenian shield centered on the outer half of the flag; the shield features a rocky coastline and three-masted sailing ship |
| Saint Kitts and Nevis | divided diagonally from the lower hoist side by a broad black band bearing two white, five-pointed stars; the black band is edged in yellow; the upper triangle is green, the lower triangle is red |
| Saint Lucia | blue, with a gold isosceles triangle below a black arrowhead; the upper edges of the arrowhead have a white border |
| Saint Martin | the flag of France is used |
| Saint Pierre and Miquelon | a yellow sailing ship facing the hoist side rides on a dark blue background with yellow wavy lines under the ship; on the hoist side, a vertical band is divided into three parts: the top part (called ikkurina) is red with a green diagonal cross extending to the corners overlaid by a white cross dividing the rectangle into four sections; the middle part has a white background with an ermine pattern; the third part has a red background with two stylized yellow lions outlined in black, one above the other; these three heraldic arms represent settlement by colonists from the Basque Country (top), Brittany, and Normandy; the flag of France is used for official occasions |
| Saint Vincent and the Grenadines | three vertical bands of blue (hoist side), gold (double width), and green; the gold band bears three green diamonds arranged in a V pattern |
| Samoa | red with a blue rectangle in the upper hoist-side quadrant bearing five white five-pointed stars representing the Southern Cross constellation |
| San Marino | two equal horizontal bands of white (top) and light blue with the national coat of arms superimposed in the center; the coat of arms has a shield (featuring three towers on three peaks) flanked by a wreath, below a crown and above a scroll bearing the word LIBERTAS (Liberty) |
| Sao Tome and Principe | three horizontal bands of green (top), yellow (double width), and green with two black five-pointed stars placed side by side in the center of the yellow band and a red isosceles triangle based on the hoist side; uses the popular pan-African colors of Ethiopia |
| Saudi Arabia | green, a traditional color in Islamic flags, with the Shahada or Muslim creed in large white Arabic script (translated as "There is no god but God; Muhammad is the Messenger of God") above a white horizontal saber (the tip points to the hoist side); design dates to the early twentieth century and is closely associated with the Al Saud family which established the kingdom in 1932 |
| Senegal | three equal vertical bands of green (hoist side), yellow, and red with a small green five-pointed star centered in the yellow band; uses the popular pan-African colors of Ethiopia |
| Serbia | three equal horizontal stripes of red (top), blue, and white; charged with the coat of arms of Serbia shifted slightly to the hoist side |
| Seychelles | five oblique bands of blue (hoist side), yellow, red, white, and green (bottom) radiating from the bottom of the hoist side |
| Sierra Leone | three equal horizontal bands of light green (top), white, and light blue |
| Singapore | two equal horizontal bands of red (top) and white; near the hoist side of the red band, there is a vertical, white crescent (closed portion is toward the hoist side) partially enclosing five white five-pointed stars arranged in a circle |
| Slovakia | three equal horizontal bands of white (top), blue, and red superimposed with the coat of arms of Slovakia (consisting of a red shield bordered in white and bearing a white Cross of Lorraine surmounting three blue hills); the coat of arms is centered vertically and offset slightly to the hoist side |
| Slovenia | three equal horizontal bands of white (top), blue, and red, with the Slovenian seal (a shield with the image of Triglav, Slovenia's highest peak, in white against a blue background at the center; beneath it are two wavy blue lines depicting seas and rivers, and above it are three six-pointed stars arranged in an inverted triangle, which are taken from the coat of arms of the Counts of Celje, the great Slovene dynastic house of the late 14th and early 15th centuries); the seal is in the upper hoist side of the flag centered on the white and blue bands |
| Solomon Islands | divided diagonally by a thin yellow stripe from the lower hoist-side corner; the upper triangle (hoist side) is blue with five white five-pointed stars arranged in an X pattern; the lower triangle is green |
| Somalia | light blue with a large white five-pointed star in the center; blue field influenced by the flag of the UN |
| South Africa | two equal width horizontal bands of red (top) and blue separated by a central green band that splits into a horizontal Y, the arms of which end at the corners of the hoist side; the Y embraces a black isosceles triangle from which the arms are separated by narrow yellow bands; the red and blue bands are separated from the green band and its arms by narrow white stripes |