The list is ordered from the oldest to the most recent announcement made by the Riot staff regarding skin sales.

Pre-Seasons Seasons
Pre-Season One Season One
Pre-Season Two Season Two
Pre-Season Three Season Three
Pre-Season Four Season Four
Pre-Season Five Season Five
Pre-Season Six Season Six
Pre-Season Seven Season Seven
Pre-Season Eight Season Eight
Early Sales


Period Sales Link
November 11
2016
November 14
2016
Galio EnchantedCircle Enchanted Galio [S|L] - 50% off
Nunu GrungyCircle Grungy Nunu [S|L] - 50% off
Gnar DinoCircle Dino Gnar [S|L] - 50% off
Quinn PhoenixCircle Phoenix Quinn [S|L] - 50% off
[1]
November 15
2016
November 18
2016
Lux SorceressCircle Sorceress Lux [S|L] - 50% off
Olaf MarauderCircle Marauder Olaf [S|L] - 50% off
Varus BlightCrystalCircle Blight Crystal Varus [S|L] - 50% off
Kha'Zix MechaCircle Mecha Kha'Zix [S|L] - 50% off
[2]
November 18
2016
November 21
2016
Shaco RoyalCircle Royal Shaco [S|L] - 50% off
Karthus PentakillCircle Pentakill Karthus [S|L] - 50% off
Zac SpecialWeaponCircle Special Weapon Zac [S|L] - 50% off
Sion WarmongerCircle Warmonger Sion [S|L] - 50% off
[3]
November 22
2016
November 25
2016
Soraka DryadCircle Dryad Soraka [S|L] - 50% off
Sejuani DarkriderCircle Darkrider Sejuani [S|L] - 50% off
Jayce DebonairCircle Debonair Jayce [S|L] - 50% off
Draven SoulReaverCircle Soul Reaver Draven [S|L] - 50% off
[4]
November 23
2016
November 30
2016
Flash & Dash Bundle - 50% off - RP icon 3187 (RP icon 5389 with champions)

Stranger Danger Bundle - 50% off - RP icon 2811 (RP icon 5013 with champions)

Otherworldly Bundle - 50% off - RP icon 2999 (RP icon 5147 with champions)

Scrappy Duelists Bundle - 50% off - RP icon 2623 (RP icon 4482 with champions)

[5]
November 25
2016
November 28
2016
Anivia BirdofPreyCircle Bird of Prey Anivia [S|L] - 50% off
Veigar VeigarGreybeardCircle Veigar Greybeard [S|L] - 50% off
Graves MafiaCircle Mafia Graves [S|L] - 50% off
Lissandra BloodstoneCircle Bloodstone Lissandra [S|L] - 50% off
[6]
November 28
2016
November 28
2016
Varus DarkStarCircle Dark Star Varus [S|L] - 28% off
Gnar ElLeónCircle El León Gnar [S|L] - 31% off
Kayle IronInquisitorCircle Iron Inquisitor Kayle [S|L] - 31% off
Taric PoolPartyCircle Pool Party Taric [S|L] - 28% off
Fizz SuperGalaxyCircle Super Galaxy Fizz [S|L] - 28% off
Kindred SuperGalaxyCircle Super Galaxy Kindred [S|L] - 28% off
[7]
November 29
2016
December 2
2016
Kog'Maw MonarchCircle Monarch Kog'Maw [S|L] - 50% off
Jax WardenCircle Warden Jax [S|L] - 50% off
Teemo CottontailCircle Cottontail Teemo [S|L] - 50% off
Fiora PROJECTCircle PROJECT: Fiora [S|L] - 50% off
[8]
December 2
2016
December 5
2016
Evelynn TangoCircle Tango Evelynn [S|L] - 50% off
Shyvana IronscaleCircle Ironscale Shyvana [S|L] - 50% off
Annie FrostfireCircle Frostfire Annie [S|L] - 50% off
Ahri PopstarCircle Popstar Ahri [S|L] - 50% off
[9]
December 6
2016
December 9
2016
Orianna SewnChaosCircle Sewn Chaos Orianna [S|L] - 50% off
Volibear RuneguardCircle Runeguard Volibear [S|L] - 50% off
Rengar NightHunterCircle Night Hunter Rengar [S|L] - 50% off
Lucian PROJECTCircle PROJECT: Lucian [S|L] - 50% off
[10]
December 6
2016
December 14
2016
Team Fire Mega Bundle - 50% off - RP icon 7570 (RP icon 13164 with champions)

Team Ice Mega Bundle - 50% off - RP icon 6345 (RP icon 10724 with champions)

[11]
December 6
2016
December 13
2016
Two rune pages for the price of one (IP icon Influence Points and RP icon Riot Points)
All boosts - 50% off
Summoner name change - 50% off

2017 Top Starter Bundle - 25% off - RP icon 2906

2017 Mid Starter Bundle - 25% off - RP icon 2906

2017 ADC Starter Bundle - 25% off - RP icon 2977

2017 Support Starter Bundle - 25% off - RP icon 3223

2017 Jungle Starter Bundle - 25% off - RP icon 3306

Siege and Poke Bundle - 50% off - RP icon 3375 (RP icon 5575 with champions)

Disrupt and Tank Bundle - 50% off - RP icon 2472 (RP icon 4113 with champions)

Style and Outplay Bundle - 50% off - RP icon 2811 (RP icon 5105 with champions)

Pick and Assassinate Bundle - 50% off - RP icon 2811 (RP icon 4867 with champions)

Stack and Scale Bundle - 50% off - RP icon 2172 (RP icon 4022 with champions)

Zone and Control Bundle - 50% off - RP icon 2511 (RP icon 4760 with champions)

Tilt Enemy or...Feed Bundle - 50% off - RP icon 2284 (RP icon 3718 with champions)

[12]
December 9
2016
December 12
2016
Maokai TotemicCircle Totemic Maokai [S|L] - 50% off
Nautilus WardenCircle Warden Nautilus [S|L] - 50% off
Darius BioforgeCircle Bioforge Darius [S|L] - 50% off
Zyra WildfireCircle Wildfire Zyra [S|L] - 50% off
[13]
December 13
2016
December 16
2016
Nidalee FrenchMaidCircle French Maid Nidalee [S|L] - 50% off
Alistar MarauderCircle Marauder Alistar [S|L] - 50% off
Gnar GentlemanCircle Gentleman Gnar [S|L] - 50% off
Vi DemonCircle Demon Vi [S|L] - 50% off
[14]
December 16
2016
December 19
2016
Gragas HillbillyCircle Hillbilly Gragas [S|L] - 50% off
Trundle JunkyardCircle Junkyard Trundle [S|L] - 50% off
Yasuo HighNoonCircle High Noon Yasuo [S|L] - 50% off
Warwick FirefangCircle Firefang Warwick [S|L] - 50% off
[15]
December 20
2016
December 23
2016
Poppy BattleRegaliaCircle Battle Regalia Poppy [S|L] - 50% off
Nunu DemolisherCircle Demolisher Nunu [S|L] - 50% off
Jinx MafiaCircle Mafia Jinx [S|L] - 50% off
Blitzcrank iBlitzcrankCircle iBlitzcrank [S|L] - 50% off
[16]
December 23
2016
December 26
2016
Ezreal FrostedCircle Frosted Ezreal [S|L] - 50% off
Jarvan IV DragonslayerCircle Dragonslayer Jarvan IV [S|L] - 50% off
Tahm Kench MasterChefCircle Master Chef Tahm Kench [S|L] - 50% off
Tryndamere SultanCircle Sultan Tryndamere [S|L] - 50% off
[17]
December 23
2016
December 26
2016
Corki ArcadeCircle Arcade Corki [S|L] - 28% off
Thresh DarkStarCircle Dark Star Thresh [S|L] - 26% off
Nami DeepSeaCircle Deep Sea Nami [S|L] - 28% off
Dr. Mundo ElMachoMundoCircle El Macho Mundo [S|L] - 28% off
Miss Fortune PoolPartyCircle Pool Party Miss Fortune [S|L] - 28% off
Kled SirCircle Sir Kled [S|L] - 31% off
Miss Fortune ArcadeCircle Arcade Miss Fortune [S|L]
Chromaskins Chromas: Amethyst, Aquamarine, Citrine, Peridot, Ruby - 33% off
Teemo CottontailCircle Cottontail Teemo [S|L]
Chromaskins Chromas: Amethyst, Aquamarine, Rose Quartz, Speckled, Turquoise - 33% off
[18]
December 27
2016
December 30
2016
Malzahar DjinnCircle Djinn Malzahar [S|L] - 50% off
Brand ApocalypticCircle Apocalyptic Brand [S|L] - 50% off
Zed ShockbladeCircle Shockblade Zed [S|L] - 50% off
Hecarim ElderwoodCircle Elderwood Hecarim [S|L] - 50% off
[19]
December 30
2016
January 2
2017
Skarner EarthruneCircle Earthrune Skarner [S|L] - 50% off
Garen RuggedCircle Rugged Garen [S|L] - 50% off
Aatrox JusticarCircle Justicar Aatrox [S|L] - 50% off
Nami KoiCircle Koi Nami [S|L] - 50% off
[20]
January 3
2017
January 6
2017
Graves HiredGunCircle Hired Gun Graves [S|L] - 50% off
Riven RedeemedCircle Redeemed Riven [S|L] - 50% off
Talon DragonbladeCircle Dragonblade Talon [S|L] - 50% off
Urgot BattlecastCircle Battlecast Urgot [S|L] - 50% off
[21]
January 6
2017
January 9
2017
Sion LumberjackCircle Lumberjack Sion [S|L] - 50% off
Soraka OrderoftheBananaCircle Order of the Banana Soraka [S|L] - 50% off
Udyr DefinitelyNotCircle Definitely Not Udyr [S|L] - 50% off
Skarner SandscourgeCircle Sandscourge Skarner [S|L] - 50% off
[22]
January 10
2017
January 13
2017
Tristana BuccaneerCircle Buccaneer Tristana [S|L] - 50% off
Sivir BanditCircle Bandit Sivir [S|L] - 50% off
Vayne DragonslayerCircle Dragonslayer Vayne [S|L] - 50% off
Illaoi VoidBringerCircle Void Bringer Illaoi [S|L] - 50% off
[23]

References

LoL's Official Sales page