Carl Zeiss of Germany are among the most renowned of lens manufacturers. It is a part of the Carl Zeiss Foundation, which also owned the Zeiss Ikon camera maker until it disappeared in 1972. The company was founded in Jena in 1856 and called Carl Zeiss Jena. Carl Zeiss Jena created such classic lens formulae as the Tessar, Planar, Biogon, and Sonnar, and equipped many camera makers, the first of which being obviously Zeiss Ikon.
After World War II, Jena being in the Eastern part of Germany, the company split in two. One part was recreated in West Germany and based in Oberkochen, and kept within the Zeiss Foundation. The other part remained in Jena, but soon lost the right to use the traditional names, like Zeiss and the other famous lens names. In the Western countries it was known as aus Jena (means from Jena), and used obvious abreviations, or other names reminding the past (for ex. T for Tessar, S for Sonnar). In the countries of the Eastern block, they continued to use the full names.
Carl Zeiss Oberkochen made lenses for the Western Zeiss Ikon after the war, but they have also made dedicated lenses for other camera marques. They continue to do so, notably for Rollei, Contax and Hasselblad.
Very recently the Carl Zeiss foundation has revived the Zeiss Ikon name for a new type of rangefinder body, and the lenses are all designed by Carl Zeiss, but some of them are manufactured by Cosina in Japan.