Enna or Enna Werk was a small German optics manufacturer, based in München, active from the 1940s to the 1980s. Enna made lenses for a number of German camera manufacturers and retailers, most notably Alpa, Balda and Porst. The company still exists, but has stopped producing camera lenses.

See their 42mm screw lenses and their Exakta lenses. They also made lenses in 39mm screw mount sold by Corfield for the Periflex, and at least one - the Ennaston 85/1.5 - in the same mount under their own name.