Death occurs when a champion takes sufficient damage to be reduced to zero health. Upon dying, the summoner's screen is shaded gray, a death recap and death timer are displayed, gold is rewarded to champions who earned a kill or an assist, and other champion or situation-specific events may occur, as detailed below. The death of all five members of a team simultaneously is referred to as an ace; it is possible for both teams to be aced at the same time, and no champions to be present on the Field of Justice.
Upon death, every player must wait a given amount of time noted over the champions image. On Summoner's Rift the death timer base can range from 10 to 52.5 seconds and will be rounded when shown when dead. The time can increase after 10 minutes in a match by 0.5% of the death timer base for every 30 seconds after 10 minutes with a cap of a 50% increase at 60:00. While the death timer is counting down, the summoner is still able to shop for items, look around the map, and chat with other teammates. Ways to reduce the length of the death timer include the following:
When the death timer reaches zero the dead champion is revived on the summoner platform.
To calculate the respawn wait time do the following:
Level × 2.5 + 7.5 = your Base Respawn Wait time (BRW) 
After minute 10, the wait time is increased from BRW as follows:
Total respawn time = BRW + (BRW / 100) × (current minutes - 10) 
After minute 60:00 the respawn time is maxed out at 150% BRW.
On Howling Abyss the death timer is based solely on level ranging from 10 to 40 seconds.
Level × 2 + 4 = Respawn time
You start on this map at level 3, resulting in an initial 10 second respawn timer.
Removal of stacks, buffs or effects
Upon death, if the champion killed possessed a buff or had built up stacks on one of a handful of items, those effects are either lost or transferred to the killer. If the champion killed possessed an innate ability, the bonus will be lost for the duration of that champion's death.
- Effects and buffs that are lost
- Buffs that are transferred to the killer
- Persistent effects lost while dead
- Stacks lost upon death (one half rounded up, unless otherwise noted)
Ways to prevent death when reaching zero health
Effects that prevent you from dying always occur in a set order:
Ways to prevent dying by not losing health
- Tryndamere's Undying Rage (can't go below 1 health)
- Kayle's Intervention (can't lose any health)
- Kindred's Lamb's Respite (can't go below 10% health)
Some champions have abilities that trigger after their death or the death of another targeted champion, allowing for limited control by one of the involved parties. These will only occur after the previously mentioned sequence and when more than one of them apply they will occur in the following order.
- Yorick's Omen of Death
- Karthus's Death Defied / Sion's Glory in Death / Kog'Maw's Icathian Surprise / Zyra's Rise of the Thorns
- Mordekaiser's Children of the Grave
When a champion is summoned to the Fields of Justice, their real, physical form is summoned there, meaning that the champions on the Fields of Justice, do, in fact die upon player death. When killed, it seems as though they are transported back to their respective summoning chambers, brought back to life, and subsequently returned to the Field of Justice to continue fighting. The following is an excerpt from Renekton's League Judgement:
"Renekton bowls through them, his blade deflecting bullets fired at point blank by a buxom redhead. A bulky minotaur slams the ground and a curiously large armadillo drops down on all fours to defend against the attack, but they are no match for the crocodile in bloodlust. The defenders are knocked aside in Renekton's mad dash for Nasus.
The creature charges up the steps, flying onto the platform with enormous momentum. Nasus reaches out to hold up his palm, as if to stop his brother, when suddenly a bright ray of light shoots out, engulfing him in an agonizing fire.
Renekton immediately succumbs to the darkness.
The creature awakens in a dark room, sprawled on a frigid stone floor. A group of cloaked magicians stand with their hands outstretched in a circle around him. They murmur strange words under their breath, ensnaring him in a glowing net of magic.
When Renekton's vision clears, he sees his brother staring dispassionately at him from across the room. Renekton snarls, throwing himself bodily towards Nasus, but the magical chains that bind him hold firm. Nasus gazes back for a long moment, his expression unreadable. Then he turns and steps into a lighted platform. "
It is also confirmed in the Journal of Justice (Volume 1, Issue 20) in the "Mailbag of Justice" section that champions are revived many times, and questions their mental state after being exposed to their own mortality day after day.