contributor; investor; financier
Refers to a person or entity that puts up money, such as an investor, donor, or financial backer. Often used in business or fundraising contexts.
This project has many contributors.
He is the main financier of the new company.
出資者 also means 'investor' or 'contributor of capital', but is more formal and often used in legal or corporate contexts. 出金者 is slightly broader and can be used for any monetary contribution.
Compound of 出金 (しゅっきん, 'withdrawal or payment of money') + 者 (しゃ, 'person'). The exact historical derivation is uncertain, but the word follows a common pattern for forming agent nouns.