Short answer. A solo parent is any individual left to raise a child alone. RA 8972 lists categories: a widow or widower, an unmarried mother or father who keeps the child, someone whose spouse is imprisoned, incapacitated, or has abandoned them, and more. Republic Act No. 11861 (2022) has since broadened this list, so check its wider terms.
What the law says
any individual who falls under any of the following categories
RA 8972, Section 3 — Who Counts As Solo Parent. Read the full provision →
The core idea: sole responsibility for a child
RA 8972, the Solo Parents' Welfare Act, defines a solo parent as any individual who falls under any of the following categories, and then lists them. The thread running through every category is the same: a person who is left carrying the responsibility of parenthood alone. It is not about being unmarried as such, but about actually bearing the day-to-day duty of raising a child without a partner sharing that load. The law also defines who the child is, generally one living with and dependent upon the solo parent for support who is unmarried, unemployed, and not over eighteen, or older but unable to support himself because of a disability.
The categories the law recognizes
The statute spells out several situations. They include a woman who gives birth as a result of rape who keeps and raises the child; a parent left alone due to death of spouse; a parent alone because the spouse is detained or serving sentence for at least one year; a parent alone due to the spouse's physical or mental incapacity certified by a public medical practitioner; and a parent alone due to legal or de facto separation, or annulment or nullity of marriage, as long as he or she has custody. It also covers an unmarried mother or father who chooses to keep and rear the child, and any other person who solely provides parental care and support.
The law has been broadened — check RA 11861
Important: the definition above is the original 2000 law, and it has been overtaken in part. Republic Act No. 11861 (2022), the Expanded Solo Parents Welfare Act, widened who qualifies as a solo parent, eased the length-of-service requirement for parental leave, and added benefits the older text does not contain, including a discount and a VAT exemption on certain purchases. So treat RA 8972's list as the floor, not the ceiling. If you are deciding whether you qualify today, or what benefits you can claim, the current terms are those of RA 11861, and the older categories should be read together with its wider ones.
Eligibility can end if circumstances change
Qualifying is not necessarily permanent. RA 8972 provides that a change in the status or circumstance of the parent claiming benefits under the Act, such that he/she is no longer left alone with the responsibility of parenthood, shall terminate his/her eligibility. So if the situation that made you a solo parent ends, for example the spouse returns or a shared-parenting arrangement resumes, the entitlement can stop. Whether you fall within a category, and whether the broadened rules of RA 11861 apply to you, depends on your actual circumstances and current issuances, so this is general information rather than advice on your specific case.