Definition
In civil law, a gestor is one who acts on behalf of another person or transacts another's business, typically without a formal appointment or express authorization. The term derives directly from Roman law and functions primarily as a descriptor of the actor in a negotiorum gestio relationship — the party who voluntarily intervenes to manage the affairs of an absent or incapacitated person.
The gestor acts not as an agent in the modern contractual sense but as a voluntary manager whose authority, obligations, and rights arise by operation of law rather than agreement. Where the intervention is lawful and conducted in good faith for the benefit of the principal (the dominus negotii), the gestor may acquire a right of reimbursement for reasonable expenses and losses incurred in the course of management.
Common Language
Modern common usage (Wiktionary): A manager of another's affairs.
Historical common usage (Webster's 1913): Not separately defined; the term did not enter general English usage.
The gap here is narrow but worth noting. The common definition captures the functional role but omits the defining legal characteristic: a gestor acts without prior authorization. An authorized manager is simply an agent. The gestor's legal significance lies precisely in the absence of prior mandate, which triggers a distinct body of civil law obligations and remedies unavailable in ordinary agency doctrine.
Common Confusion
GESTOR vs. AGENT: These terms are frequently used interchangeably in loose translation but describe fundamentally different legal relationships. An agent acts under express or implied authority conferred by a principal; the agent-principal relationship is consensual and contractual. A gestor acts without prior authority, and the legal relationship that arises is quasi-contractual, imposed by law upon both parties once the intervention occurs. Substituting "agent" for "gestor" in historical civil law sources will misread the nature of the obligation being described.
NEGOTIORUM GESTOR vs. GESTOR: Gestor is the broader term, capable of describing any person who acts for another. Negotiorum gestor is the technically precise civil law phrase referring to the specific doctrine of unauthorized management of another's affairs. Most legal dictionary entries and treatise discussions use the full phrase; bare "gestor" most often appears as shorthand within a negotiorum gestio analysis.
Why It Matters in Research
Researchers will encounter gestor almost exclusively in two contexts: Roman law scholarship and civil law jurisdictions that preserved or codified the negotiorum gestio doctrine, including Louisiana, Quebec, Scotland, and the civil law systems of continental Europe and Latin America.
In common law sources, the term appears rarely and typically signals that the author is drawing on civil law analogies — often to explain restitutionary or quasi-contractual liability. When gestor appears in English-language common law texts before the twentieth century, treat it as a civil law borrowing rather than a term of art within that jurisdiction's domestic doctrine.
The historical dictionaries consistently cross-reference Negotiorum gestor as the operative term. Researchers who encounter gestor as a standalone entry should proceed directly to that article for substantive doctrine. The reimbursement rights of the gestor, the standard of care required, and the conditions under which the dominus is bound by the gestor's acts vary meaningfully across civil law systems and across time periods within Roman law itself — distinctions the bare dictionary entry does not resolve.
One indexing trap: older digests and abridgments may file gestor-related material under Agency, Mandate, or Quasi-Contract rather than under any Latin heading. Louisiana jurisprudence and doctrinal writing is the most accessible English-language body of law for negotiorum gestio analysis and will be the most useful corpus entry point for common law researchers seeking analogical guidance.
Historical Dictionary Support
All three source dictionaries converge on the same one-line definition: one who acts for another or transacts another's business. All three trace the term to civil law. Burrill adds the etymological root (gerere, to act) and the explicit cross-reference to Negotiorum gestor, making his entry the most useful of the three for navigating to substantive doctrine. Both editions of Black's cite Calvin's Lexicon Juridicum as authority — a seventeenth-century civil law reference work — which reflects the term's identity as a term of Roman law scholarship rather than living practice in Anglo-American courts.
The second edition of Black's contains an anomalous passage describing an heir's liability to a deceased's creditors through acts of intermeddling. This passage appears to be a garbled insertion (likely misplaced text from an entry on pretermission or heres), and should not be read as a modification of the gestor definition. The operative definition in that edition is the final sentence, which matches the first edition exactly.
None of the historical dictionaries addresses the rights of the gestor — only the role. Researchers needing the doctrinal content of negotiorum gestio, including the conditions for reimbursement and the obligation to account, must look beyond these dictionary entries to treatise and code sources.
Jurisdictional Note
The gestor doctrine has no direct common law equivalent, though courts in equity and restitution have reached analogous results under theories of necessitous intervention, salvage, and unjust enrichment. In mixed and civil law jurisdictions — Louisiana (Civil Code art. 2292–2297), Quebec (Civil Code art. 1482–1490), and Scottish law — the doctrine is codified and the term negotiorum gestor remains doctrinally operative. Common law researchers should not assume that results in these jurisdictions will transfer without doctrinal adjustment.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Negotiorum Gestio (primary); Agency — Formation and Authority (for contrast with authorized representation); Quasi-Contract and Unjust Enrichment (for common law analogues).