The First Speaker of the Detapa Council was the leader of the Detapa Council in the Cardassian Union prior to the 2371 Cardassian coup. The position held little power due to the Cardassian Central Command's executive powers, but could at times be used to control Central Command's funding. (TLE novel: The Art of the Impossible) After the 2371 coup, the leader of the Detapa Council -- and therefore of the Cardassian Union -- was titled Chief Executor. (DS9 novel: The Never-Ending Sacrifice)
In 2318, the First Speaker claimed that followers of the Oralian Way were in charge of the diplomatic mission to Bajor, but in reality the military was in control. (TLE - Terok Nor novel: Day of the Vipers)
In an alternate timeline, the First Speaker was Kotan Pa'Dar, who sent a subspace message to the leaders of local space that the Cardassian Union had annexed the Ferengi Alliance. (Myriad Universes novel: A Gutted World)