Yvette Gessard-Picard was a Human woman who lived in La Barre, France during the early 24th century. She was the wife of Maurice Picard, the mother of Robert and Jean-Luc Picard, and the paternal grandmother of René Picard. Yvette was deceased by 2364. Jean-Luc affectionately referred to her as "Maman".
Yvette used to sing "come out, come out wherever you are" to Jean-Luc when he was a young child. (Star Trek: Insurrection)
While in a distant section of the universe where thoughts become reality, Jean-Luc Picard experienced a brief vision of his mother. (TNG: "Where No One Has Gone Before")
As a child, Captain Picard took piano lessons; though he seemed antipathetic to them, in later life he regretted giving them up, as they pleased his mother. (TNG: "The Perfect Mate")
Yvette was played by Herta Ware.
Her name was mentioned in TNG: "Chain of Command, Part II", and was a homage to actress Yvette Mimieux, who starred in the 1960 film The Time Machine. (Star Trek Encyclopedia 2nd ed., p. 361)
Yvette spoke English with a French accent, while Captain Picard, his father and brother spoke English with typically English accents.
A picture of Yvette was included on a page of the Picard family album that did not make it on screen.