Single-8, also known as 8 mm Type S, Model II, is a motion picture film format introduced by Fujifilm of Japan in 1965 as an alternative to the Kodak Super 8 format. Single-8 and Super 8 use mutually incompatible cartridges, but the 8 mm film within each cartridge shares the same frame and perforation size and arrangement, so developed Single-8 and Super 8 films can be shown using the same projection equipment.
Although never as popular internationally as Super 8, the format continued to live in parallel. Fuji discontinued the manufacture of Single-8 film by 2012. The two final Single-8 film cartridge types produced by Fuji were Fujichrome R25N, discontinued in 2012, and Fujichrome RT200N, discontinued in 2010. Single-8 proved to be quite successful in Japan, capturing 80–85% of the domestic market for home movies until 1973, At least one camera was made which accepted both Single-8 and Super 8: the Honeywell Elmo Tri-Filmatic Super 100, manufactured in Japan by Elmo and sold in different countries as the Elmo C300, which uses interchangeable magazines for Regular (Double) 8, Super 8, Single-8, and 100-ft reels of Double Super 8.
Fuji announced it would cease production of 8 mm film in 2006, but reversed that decision in 2007. While the Single-8 film is more resistant to breakage, it tends to stretch if the film transport jams. Rewinding enables in-camera special effects, including dissolves, multiple exposures, and title sequences.
The Single 8 cartridge was designed with an open section for the film, allowing it to be fed between the pressure pad and film gate, both part of the camera, during exposure. This contrasts with the Kodak system which had a plastic pressure plate built into the cartridge. In addition, like the notches on Super 8 cartridges, the Single-8 cartridge has several tabs, slots, and holes to automatically set film speed and type.
[[File:S8M2 cartridge (Single-8).svg|thumb|right|upright=1.3|Single-8 cartridge with relevant indicators:
<ul>
<li>s1: Film speed indication tab; position relative to surface (T* dimension) varies with film speed.</li>
<li>s2: Film speed indication grooves; length of groove (J* or θ*) varies with film speed.</li>
<li>ID1: Film type / filter indication hole</li>
<li>ID2: Film type / filter indication tab</li>
</ul>]]
{|class="wikitable" style="font-size:90%;text-align:center;"
|+Single-8 cartridge film speed indicators