There are multiple definitions - click on the translation that matches your context.

Anteilseigner

Substantiv

full

shareholder

noun

Comparative law notes

Austria

Since "Anteil" literally means proportion/quota, if the context does not involve corporate entities, then the better translation would be "part owner" , "partner" or even "owner" (when there is only a single Anteilseigner).

Definitions of shareholder

English

an person, company or organisation that owns shares in a company

Shareholders of a company are not personally liable for the company's debts beyond their investment in the shares.