| Clubname: | Clube Atlético Operário |
| Nickname: | Glorioso Alvinegro do Planalto Norte Alvinegro Catarinense |
| Fullname: | Clube Atlético Operário |
| Founded: | December 8, 1940 |
| Ground: | Estádio Alfredo Herbst, Mafra, Santa Catarina state, Brazil |
| Capacity: | 3,000 |
| Chrtitle: | President |
| Mgrtitle: | Head Coach |
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Clube Atletico Operário, commonly former EC Operário de Mafra, is a Brazilian football club based in Mafra, Santa Catarina state. The club was formerly known as Sociedade Esportiva e Recreativa Operários Mafrenses and Clube Atlético Operário.
The club was founded on May 12, 1897,[1] is Clube Atlético Operário, in the 1990s it was renamed to Sociedade Esportiva e Recreativa Operários Mafrenses, but the club's logo still depicts the acronym CAO, meaning Clube Atlético Operário.[2] They won the Campeonato Catarinense Third Level in 1913, 1947, 1996.
Clube Atlético Operário play their home games at Estádio Alfredo Herbst. The stadium has a maximum capacity of 3,000 people.