This is an overview of Skyrim's alchemical ingredients (also called "alchemy reagents").
More information on each ingredient can be found on its individual page (see links in the tables below). UESP's Skyrim Map and UESP's Dragonborn Map have the functionality to show the location of plants in Tamriel world space.
The Alchemy Effects article lists ingredients indexed by magical effect and contains additional information about the relationships between ingredients, alchemy, and magical effects. A few ingredients are also classified as food.
General merchants usually offer a few ingredients. Apothecary merchants offer many more, each stocking:
Up to 15 common ingredients
Up to 10 uncommon ingredients
Up to 5 rare ingredients
Counter to intuition, your chances of finding a specific uncommon ingredient in an apothecary's stock are smaller than those for finding a rare ingredient. This is because there are so many more uncommon ingredients than rare ingredients, that: [(# of uncommon ingredients offered/total # of uncommon ingredients) < (# of rare ingredients offered/total number of rare ingredients)].
Some ingredients can be bought and sold only if the merchant perk has been unlocked on the Speech perk tree.
Already-harvested samples
You can find some ingredients on shelves or tables, in baskets, pots, etc., in various locations throughout Skyrim. They are typically plentiful in apothecaries' businesses and living quarters. Their owners may let you take the relatively inexpensive of these for free if you have done them favors. Mages and wizards around Skyrim, a concentration of which are people living at the College of Winterhold, tend to possess ingredients in their dwellings and rooms.
Some types of NPCs and enemies may carry ingredients on their person.
Ingredients can also be found in containers.
Certain barrels contain multiple copies of a common ingredient.
Apothecary's satchels always contain one or more randomly-selected ingredients (plus a 25% chance of containing a healing potion). These satchels are tagged internally in the game as of common-, uncommon-, or rare-type. Rare-type satchels always contain one common, one uncommon, and one rare ingredient.
Harvesting from plants
You can take ingredients from many of Skyrim's plants. Some of these are common and widespread, with thousands of plants growing in diverse areas, whereas others are quite rare and difficult to find. Once you have harvested a plant's ingredient, some or all of its flowers and stems disappear, allowing already-harvested plants to be easily identified. Harvested plants will later respawn, at which point you can again harvest their ingredients.
Collecting from creatures
Many creatures' body parts—meat, wings, heart, skin, horns, teeth, etc—are alchemy ingredients. When you kill the creature, you can collect the ingredient from its corpse.
Catching passive creatures
Various passive creatures can be caught to obtain ingredients, including bees, fish, dragonflies, torchbugs, and butterflies.
With Hearthfire installed, areas of fertile soils can be added to the homesteads. These soils can be planted with a sample. The plant will grow into maturity after typically 2 days and there will be 2-5 samples of the ingredient on each plant (depending on the plant). The plant will not die and will respawn every few days after harvesting. However, not all plant ingredients can be planted. A list of plants that can be grown may be found here.
Standard Ingredients
This table lists all of the standard ingredients in the game. You will experience a mild primary effect from eating an ingredient. Brewing two or more ingredients that share magical effects at an alchemy table will result in a potion or poison, with higher Alchemy skill levels resulting in stronger effects—longer duration, better fortifications or damage, etc. Special items such as Daedric Hearts and Void Salts are used in smithing Daedric equipment and improving Nightingale armor, respectively.
Cannot be harvested or collected in the original version of the game; only readily available after the Merchant perk has been unlocked. With Dragonborn, they can be harvested from Pearl Oysters in Solstheim.
Cannot be harvested or collected in the original version of the game; only readily available after the Merchant perk has been unlocked. With Dragonborn, they can be harvested from Pearl Oysters in Solstheim.
These ingredients are of limited value for alchemy: some of them can't be used in alchemy (even though the game labels them as ingredients) and they have a very limited number of possible samples.
Damage Stamina
Resist Fire
Resist Frost
Restore Magicka
Weakness to Shock