CSS-1 Corellian Star Shuttle
The CSS-1 Corellian Star Shuttle, alternatively referred to as the Republic shuttle, functioned as a starship specifically engineered for the transportation of numerous ambassadors on various missions throughout the galaxy.
Characteristics

Compared to the Consular-class cruiser, the CSS-1 Corellian Star Shuttle offered increased internal space and passenger capacity. A sizable conference room was also a key feature. Given their role as diplomatic vehicles, Star Shuttles were unarmed, but they were equipped with a robust deflector shield.
This class of vessel was produced by the well-known Corellian Engineering Corporation, responsible for the majority of ships utilized by the Galactic Republic. Their extensive armor plating contributed to them being less adaptable than typical CEC designs.
This transport required a crew consisting of a captain, two co-pilots, a pair of communications specialists, and three engineers. It was capable of carrying roughly 200 passengers and 900 metric tons of cargo.
History
In the Republic's final decades, Star Shuttles were utilized as diplomatic vessels, but some were adapted for military purposes, receiving at least two turbolasers. They saw action in the Judicial Forces and participated in conflicts such as the Stark Hyperspace War, the Yinchorri Uprising, and the Clone Wars. The Corellian Star Shuttle named Perpetuus was used to transport Chancellor Palpatine to Theed following the Battle of Naboo.

Following the Republic's transformation into the Empire, many Star Shuttles fell into private ownership. A Star Shuttle, at least one, was used to create a secret retreat in 137 ABY.
Behind the scenes
Dan Wallace revealed on his blog that Palpatine's shuttle was given the name Perpetuus in The Essential Guide to Episode I. However, as the book was never published, the name is considered non-official. The sourcebook Suns of Fortune identified the Corellian Star Shuttle with the full designation "CSS-1 Corellian Star Shuttle," although it was mistakenly written as CCS-8 in one instance.