The first three seasons of The Mandalorian contain 24 episodes in total. Each season has eight episodes, so the arithmetic is 8 + 8 + 8 = 24.
The series premiered on Disney+ in November 2019, with later seasons arriving in 2020 and 2023. Its episodes are commonly labeled “Chapters,” beginning with “Chapter 1: The Mandalorian” and reaching “Chapter 24: The Return.”
A common mix-up is confusing the show’s chapter numbering with the number of seasons, or counting related Star Wars programs such as The Book of Boba Fett. Those are separate series, even though The Book of Boba Fett contains important Mandalorian story developments.