Evolution Items

Evolution Items are items necessary to evolve certain species of Pokémon. There are currently eight items that can be obtained in game:
 * Sun Stone
 * King's Rock
 * Metal Coat
 * Dragon Scale
 * Up-Grade
 * Sinnoh Stone
 * Unova Stone
 * Gimmighoul Coins

For Trainers to see the Evolution Items that they currently own, they have to check their Item Bag page.

Johto items
All of the items originally introduced in the Johto region have a small chance of being obtained from spinning Photo Discs in PokéStops and Gyms. Trainers are also guaranteed one from completing a seven day spin streak. They can also be obtained as rewards from research tasks and gifts.

Sinnoh Stone
Sinnoh Stones can be obtained by claiming Research Breakthrough rewards or from participating in Trainer Battles.

Unova Stone
Unova Stones can be obtained by claiming Research Breakthrough rewards or from defeating Team GO Rocket Leaders.

Gimmighoul Coins
Gimmighoul Coins can be obtained by catching or walking with Gimmighoul and from spinning Golden PokéStops.

Trivia

 * The Porygon family is the only evolutionary line that requires two different Evolution Items to evolve, one for each stage.
 * Gimmighoul Coins are the only Evolution Items not to also require Candy to evolve the Pokémon its compatible with.
 * Gimmighoul Coins originally appeared after Community Day Classic: Dreaming of Dratini for a tie-in event with Pokémon Scarlet and Pokémon Violet. They were originally referred to as ?????? Coins.
 * All Pokémon that result from an item evolution cannot be caught in the wild, hatched from an Egg, be a Raid Boss, or be a reward obtained from research tasks under normal conditions, and the only way to acquire them is through item evolution.
 * The only exceptions are Pokémon spawned by using a Daily Adventure Incense, or appearing as Mega Raid Bosses or event-related Raid Bosses.
 * Historically in the core-series of Pokémon games, Pokémon that evolve with a Dragon Scale, a King's Rock, a Metal Coat, or an Up-Grade must be traded while holding the item in order to trigger the evolution process.
 * Pokémon that evolve by holding a Sun Stone, on the other hand, do not need to be traded to the process is triggered.
 * On the official support page for Pokémon GO, Deepsea Tooth and Deepsea Scale were mentioned.
 * In the main series games, these items are required to evolve Clamperl into either Huntail or Gorebyss respectively.
 * This concept was scrapped and the evolution of Clamperl was decided to be random.
 * The Sinnoh Stone was first discovered in network traffic on November, 2018.
 * The design of the Sinnoh Stone suggests that it is composed of diamond and pearl-like materials, which is a reference to the Pokémon: Diamond and Pearl games, in which the Sinnoh region was first introduced.
 * Similar to the Sinnoh Stone, the Unova Stone is composed of black and white materials, which is reference to the Pokémon: Black and White games, in which the Unova region was first introduced.
 * Sinnoh Stones were guaranteed Research Breakthrough rewards during Hatchathon 2018.
 * During the February 2019 Community Day, Trainers were guaranteed to receive up to five Sinnoh Stones as a reward from Trainer Battles; in order to evolve their Piloswine into Mamoswine.
 * No Sinnoh Stone was guaranteed on August 2019 Community Day for evolving Kirlia into Gallade.
 * During the February 2020 Community Day, Trainers were guaranteed to receive two Sinnoh Stones as a reward from one set of GO Battle League completed; in order to evolve their Rhydon into Rhyperior.