The invention relates to a phytase derived from Citrobacter gillenii and related phytases. The phytases belong to the acid histidine phosphatase family, are acid-stable, and expectedly of a high specific activity. The invention also relates to the corresponding DNA, the recombinant and wild-type production of the phytases, as well as the use thereof, in particular in animal feed, for example in combination with phytases having a higher pH-optimum.