Endurance( Player's Handbook v.3.5, p. 93)
You are capable of amazing feats of stamina.
Controlled Respiration (SS) , Death Frenzy (LoM) , Diehard (PH) , Epic Endurance (ELH) , Epic Spellfire Wielder (PG) , Expert Swimmer (SW) , Indomitable Soul (PH2) , Lasting Life (LM) , Remain Conscious (MW) , Remain Conscious (SF) , Shifter Stamina (RoE) , Steadfast Determination (PH2) , Strong Stomach (Ci) , Hibernate (DC) , Diehard (Gh) , Lasting Life (Rav) , Remain Conscious (OA) ,
You gain a +4 bonus on the following checks and saves: Swim checks made to resist nonlethal damage (see page 84), Constitution checks made to continue running (see page 144), Constitution checks made to avoid nonlethal damage from a forced march (see page 164), Constitution checks made to hold your breath (see page 84), Constitution checks made to avoid nonlethal damage from starvation or thirst (see page 304 of the Dungeon Master's Guide), Fortitude saves made to avoid nonlethal damage from hot or cold environments (see pages 302 and 303 of the Dungeon Master's Guide), and Fortitude saves made to resist damage from suffocation (see page 304 of the Dungeon Master's Guide). Also, you may sleep in light or medium armor without becoming fatigued.
A ranger automatically gains Endurance as a bonus feat at 3rd level (see page 48). He need not select it.
A character without this feat who sleeps in medium or heavier armor is automatically fatigued the next day.