An ownership interest refers to any type of legal right or claim that an individual, group, or entity has in a property, asset, or business. This can include shares in a company, stocks, bonds, deeds, and other forms of title. It represents the extent to which someone has a stake in something, and can be used as a measure of how much control they have over it. In essence, an ownership interest is a reflection of one's rights and responsibilities with regards to a particular asset or investment.