In the Song of the Lioness quartet, Alanna of Trebond is one of the main protagonists. The series follows her journey from a tomboyish girl posing as a boy in order to become a knight, to one of the most skilled warriors in the kingdom. Along the way, she falls in love with Prince Jonathan and they eventually get married.
The series is set in Tortall, a fictional country that is based on medieval Europe. It is clear from early on that Alanna has no interest in getting married or being lady-like; she just wants to be a knight like her father before her. However, fate has other plans and she meets Jonathan when he comes to Trebond to learn swordsmanship from her father (who doesn't know she's really a girl). They become friends, but things change when Jonathan becomes heir to the throne and Alanna starts training at the palace as his bodyguard.
Their relationship deepens and they eventually confess their love for each other, but because Jonathan is betrothed to another woman ( Princess Thayet of Sarain), they cannot be together openly. Things come to a head when Thayet is kidnapped by pirates and Alanna goes after her, risking her life to save Jonathan's future wife. This act finally convinces Jonathan that he loves her enough to break off his engagement and marry her instead.
Alanna and Jonathan have a happy ending - they get married and rule Tortall together for many years - but it's not always easy. As noted earlier, Alanna isn't interested in being queen or living a traditional life; she much prefers adventuring and spending time with her friends (especially George Cooper) than attending court functions or hosting dinner parties. Luckily, Jonathan understands this about her and lets her do what she wants most of the time, even though it often means he's left home alone while she gallivants around the kingdom!