Lithium hydroxide is an inorganic compound with the formula LiOH. It can exist as anhydrous or hydrated, and both forms are white hygroscopic solids. They are soluble in water and slightly soluble in ethanol. Both are available commercially. While classified as a strong base, lithium hydroxide is the weakest known alkali metal hydroxide.

The preferred feedstock is hard-rock spodumene, where the lithium content is expressed as % lithium oxide.

Lithium hydroxide is often produced industrially from lithium carbonate in a metathesis reaction with calcium hydroxide:

The initially produced hydrate is dehydrated by heating under vacuum up to 180 °C.

An alternative route involves the intermediacy of lithium sulfate:

The main by-products are gypsum and sodium sulphate, which have some market value.

According to Bloomberg, Ganfeng Lithium Co. Ltd. (GFL or Ganfeng) and Albemarle were the largest producers in 2020 with around 25kt/y, followed by Livent Corporation (FMC) and SQM. Significant new capacity is planned, to keep pace with demand driven by vehicle electrification. Ganfeng are to expand lithium chemical capacity to 85,000 tons, adding the capacity leased from Jiangte, Ganfeng will become the largest lithium hydroxide producer globally in 2021.

Albemarle's Kemerton, Western Australia plant, originally planned to deliver 100kt/y has been scaled back to 50kt/y.