What legal term describes a person who has been designated to manage someone else's affairs?

The term that describes a person who has been designated to manage someone else's affairs is conservator. A conservator is specifically appointed to oversee an individual's financial or personal matters when that individual is unable to do so due to a variety of reasons, such as incapacity or disability. This designation typically occurs through a legal process, where the court determines that the individual requires assistance to manage their affairs responsibly.

While a guardian might also manage affairs, their role is generally more focused on personal welfare, particularly for minors or individuals lacking the capacity to make decisions about their personal well-being. A trustee, on the other hand, is responsible for managing trust assets on behalf of beneficiaries, which is a different legal role entirely. An executor is tasked with carrying out the provisions of a will after someone has passed away, which does not encompass managing affairs during a person’s lifetime. Thus, conservator is the most precise term for managing another's affairs under the circumstances described.