David Catania has been a D.C. Council member since 1997, when he won a special election.
Council member David Catania (I-At Large) will be the latest District of Columbia politician to enter the race for mayor.
Ben Young, Catania's former chief of staff who is working on his campaign, said Monday night that Catania will file papers to run later this week.
Catania is an independent and will challenge the Democratic primary winner in the November general election. He was first elected to his at-large council seat in 1997 and is one of two openly gay council members.
The Democratic primary field includes Mayor Vincent Gray and seven challengers.
Earlier Monday, federal prosecutors alleged in court documents that Gray was aware of an illegal "shadow campaign'' that aided his 2010 bid and requested the funds personally. Gray says the allegations are false.
A recent WAMU/NBC4 poll found that Catania was in a statistical tie with Gray in a hypothetical general election matchup.