What is Morty Smith's full first-and-middle name?

Morty Smith’s full first-and-middle name is Mortimer Chauncey.

“Morty” is a familiar nickname for Mortimer, the anxious teenager who shares the series title with his grandfather Rick. Character listings give his full name as Mortimer Chauncey Smith Sr., so the requested first and middle names are Mortimer Chauncey.

Morty is the son of Beth Smith and Jerry Smith, the younger brother of Summer Smith, and Rick Sanchez’s grandson. He is usually identified simply as Morty in dialogue, which is why many viewers never encounter his formal name during ordinary episodes.

The “Sr.” suffix is another potential source of confusion. It is part of the character’s listed full name, but it is not part of the first-and-middle answer asked here. Likewise, Smith is his surname, not part of the requested first-and-middle portion. The canonical answer is therefore “Mortimer Chauncey,” rather than an invented expansion of the nickname or a variation on the Smith family names.