Chivalry (騎士道 Kishi Michi lit. Way of the Knight in the Japanese version, Chevalerie in the French version) is the Personal Skill of Xander in Fire Emblem Fates.
If Xander attacks an enemy whose HP is at maximum, he will deal an additional 2 damage to his attack and will receive 2 less damage. If Xander double attacks, the second attack will retain the bonus damage and will retain the bonus damaged shaved if counter attacked. It will not reduce damage received from Counter related skills.
Chivalry is the inverse of Pragmatic, Leo's personal skill, as Chivalry receives its boost when Xander faces an enemy whose HP is at maximum, while Pragmatic does if Leo faces an enemy whose HP is not at maximum.