Definition
1. Of a person: Born to parents who were not lawfully married to each other at the time of birth; a child born out of wedlock. The historical legal consequence was significant: an illegitimate child was treated as filius nullius — the child of no one — with no right to inherit from either parent under the common law and no recognized legal relationship to the father absent formal acknowledgment or adoption.
2. Of an act, authority, or instrument: Contrary to law; unauthorized; not sanctioned by legal authority. A government act may be condemned as illegitimate if it exceeds constitutional bounds; a contract may be illegitimate if its object is prohibited by law.
The first meaning has dominated legal usage and generated the bulk of doctrine. The second meaning shades into more general usage and is discussed below.
Common Language
Modern common usage (Wiktionary): A person born to unmarried parents.
Historical common usage (Webster's 1913): Not according to law; not regular or authorized; unlawful; improper. Also: unlawfully begotten; born out of wedlock; bastard.
The common and legal meanings align closely for the personal-status sense, but the gap lies in consequence. In ordinary usage, "illegitimate" describes a biographical fact carrying modest social significance. In historical legal usage, it was a status with sweeping disabilities — bars to inheritance, inability to claim a father's name, exclusion from family entitlements, and, in some jurisdictions, incapacity to hold certain offices. Modern law has largely dismantled these consequences, so the term now carries far more weight in historical sources than in contemporary practice.
Common Confusion
ILLEGITIMATE vs. BASTARD: The terms were used interchangeably in most historical dictionaries and case law. "Bastard" was the technical common-law term of art; "illegitimate" was its civil-law and statutory equivalent, and in many civilian jurisdictions carried a more granular classification system. Modern legal drafting has retired both terms in favor of neutral formulations such as "nonmarital child" or "child born out of wedlock." Researchers encountering either term in historical sources should treat them as functionally synonymous but should note that "bastard" carries specific common-law procedural history (bastardy proceedings, the writ de bastardía) that attaches less cleanly to "illegitimate."
ILLEGITIMATE vs. NATURAL CHILD: "Natural child" was frequently used as a softer synonym for illegitimate child, particularly in civil-law jurisdictions. In Louisiana and in French and Spanish legal traditions, "natural child" could also denote the more favorable subcategory of illegitimate children — those whose parents could have lawfully married. The terms are not always interchangeable. Context and jurisdiction govern.
Recognized Forms
/SUBTYPES
Louisiana's civil-law tradition, reflected in both editions of Black's, formally subdivided illegitimate children:
1. Natural children: Born of two persons who, at the moment of conception, were legally capable of marrying each other. These children could be legitimated by the subsequent marriage of their parents or by formal acknowledgment, and they enjoyed limited inheritance rights.
2. Spurious children: Born of persons whose marriage was legally impossible at the time of conception — due to an existing marriage, prohibited degree of relationship, or other impediment. This subclass included adulterine children (born of adultery) and incestuous children. Their legal disabilities were more severe and legitimation was often unavailable.
This civil-law taxonomy did not transplant into the common law, which treated all children born outside lawful marriage as a single undifferentiated class.
Why It Matters in Research
This term is a historical-evolution term. Researchers must treat "illegitimate" as a term whose legal consequence has changed dramatically, not merely whose definition has shifted.
In pre-20th-century sources, the term carries an enormous freight of disability law — inheritance bars, bastardy proceedings, legitimation statutes, and canon law overlay on civil status questions. A finding in an 1870 treatise or court opinion that a child is "illegitimate" means something categorically different from the same finding in a 2000 opinion, where it may carry no legal consequence at all.
Constitutional transformation matters: The U.S. Supreme Court beginning in the late 1960s applied Equal Protection scrutiny to classifications based on illegitimacy, progressively dismantling the disability structure that historical sources take for granted. Researchers relying on historical sources to understand current law risk importing obsolete rules wholesale.
Jurisdictional traps: The common law / civil law divide is acute here. Louisiana sources, and any source touching French, Spanish, or Mexican legal heritage, use a different classificatory system. The natural child / spurious child distinction appears in Louisiana statutes and cases but will look alien in common-law research.
Corpus connections: Legitimacy questions appear densely in probate and intestacy materials, paternity and bastardy proceedings, legitimation by marriage or acknowledgment, immigration and citizenship records (where legitimacy determined derivative citizenship status), and inheritance tax materials. Researchers tracing a particular individual's status through historical records will encounter all of these bodies of law.
Historical Dictionary Support
The historical dictionaries converge on the personal-status meaning as primary, with "contrary to law" offered as a secondary gloss. Black's (both editions) and Bouvier share nearly identical text, both sourcing to the Louisiana civil-law classification — which is notable because Louisiana's taxonomy is not representative of American common law generally. That Black's foregrounded the Louisiana subdivision suggests the civilian distinction was considered editorially useful, not that it was nationally operative.
Burrill is the most spare, pointing readers to Kent's Commentaries for elaboration — a useful research pointer, as Kent's treatment of the common-law rules on illegitimacy and inheritance remains an authoritative secondary source for pre-Civil War American law.
Anderson directs readers to LEGITIMATE without independent analysis, which is consistent with that dictionary's cross-referencing style but unhelpful for researchers encountering the term in isolation.
None of the historical dictionaries engage with what "illegitimate" means in the sense of unauthorized governmental or institutional action — a usage that, while present in Webster's 1913, appears to have been treated by legal lexicographers as too diffuse to warrant a standalone definition.
Jurisdictional Note
The common-law states treated illegitimacy as a unitary status with near-total inheritance disability, while civil-law states (principally Louisiana) maintained the natural/spurious distinction with differentiated legal consequences. Modern uniform acts (including the Uniform Parentage Act in its various versions) have effectively replaced the term in statutory law with non-status-based frameworks. Researchers in states that adopted the UPA at different times should verify which version governs a given period.
Encyclopedia Cross-Reference
Law Mind Encyclopedia — Legitimacy
Law Mind Encyclopedia — Bastard
Law Mind Encyclopedia — Parent-Child Relationships