FE8 introduced branching promotion paths to the series. All classes that are able to promote will have 2 possible promotion options. The Trainee classes were also introduced, which can promote into two regular unpromoted classes or the Super Trainee class, giving them 3 different branching options.

Eirika and Ephraim have their promotions locked behind a story event, and can promote at the end of Chapter 16. Should the player decline, their special promotion items will be in their respective inventories, ready to use at any time.

Promotion stat bonuses generally follow the same pattern as FE7, they typically will attempt to make up for units' weaker stats. FE8 also has a special case, where Ewan (Pupil) will lose all Anima rank when they promote to Shaman. This is the only case in the GBA games where units lose weapon rank upon promotion.

FE8 also has gendered classes, although there are a few oddities.

Due to the branching promotion system and the existence of trainees, most fully promoted classes will have both male and female instances existing in the base game. However, there are a few exceptions. There can never be a female Wyvern Lord, because there are no female Wyvern Riders and Tana and Vanessa can only promote into Wyvern Knights. There can never be a female Druid/Summoner.

This page lists all classes in FE8 (including NPC and monster classes), organized into unpromoted and promoted classes. The differences between male/female classes are not listed here, click into an individual class to see that data along with promotion stat bonuses.