Cosina Co., Ltd. (株式会社コシナ, Kabushiki-gaisha Koshina^?) is a designer and manufacturer of cameras and lenses, and a glassmaker, based in Nakano, Nagano Prefecture, Japan.

Cosina is the successor to Nikō (or "Nikoh"), a company set up as a manufacturer of lenses in 1959. In 1966, it started to manufacture 35 mm compact cameras and 8 mm cine cameras, in 1968 it started a glassworks, and a year later started the manufacture of 35 mm film SLR cameras. Nikō changed its name to Cosina in 1973. (The first part of the name is a reference to the Koshi area within Nakano, where the founder came from; while the 'Na' represents Nakano.)

The name Cosina has previously appeared on compact and SLR cameras for 135 film. The CS-2 and CS-3 SLRs were introduced in 1978, followed in 1980 by the CT-1, CT-7 (The world's first all—push-button SLR), CT-10 and CT-20, the CT-1G in 1982 and the CT-9 in 1986. Cosina SLR cameras used either the M42 (Praktica/Pentax) lens mount or the Pentax K (bayonet) lens mount. However Cosina is probably better known as a manufacturer of cameras and camera components for other brands. During the late 1970s, Cosina made a name for itself in 35 mm rangefinder cameras with a well-built, high quality fixed-lens camera using an aluminum body and a simple shutter-priority autoexposure system. This rangefinder camera was adopted as the basic chassis for several excellent camera models, including the Konica Auto S3, Minolta 7sII, Revue 400se, Prinz 35ER, and Vivitar 35ES.