Illiteracy -- the inability to read or write -- certainly puts you at a disadvantage in the job market. Nevertheless, illiteracy alone doesn't qualify as a "disability" that would allow an adult to collect benefits from programs for people who are unable to work. If illiteracy is the result of a medical condition, though, you might be able to make a case that you have a disability.
The federal Americans with Disabilities Act, or ADA, provides the primary guidance for what constitutes a disability. The law doesn't actually list conditions that qualify as disabilities, but it provides a general definition that you can apply to your condition to see whether it meets the standard. Under the law, a disability is any "physical or mental impairment" that affects your ability to participate in one or more "major life activities." Reading is among the activities identified in the law, so illiteracy, by definition, affects a major life activity. The question is whether illiteracy is an "impairment."
According to the Society for Human Resource Management, the simple fact that an adult cannot read or write doesn't qualify as a disability under the ADA. Illiteracy becomes a disability only if it is the result of a physical or mental impairment. For example, if you suffer a stroke or severe head trauma that leaves you unable to read, that's a disability. If you have a severe learning disability that made it impossible to learn to read, that also qualifies as a disability. However, if you have the ability to learn to read but just never did so because of "social, cultural and economic" factors, you're not disabled. Examples might be someone who never went to school, went to a bad school or can only read a language other than English.
State Disability Benefits
Only five states have disability benefits programs: California, Hawaii, New Jersey, New York and Rhode Island. Puerto Rico, a U.S. territory, also has a program. These are short-term programs, funded by payroll taxes, that provide cash benefits to workers who suffer an off-the-job illness or injury that leaves them unable to work. If you live in one of these states and can demonstrate that you have suffered a qualifying impairment that left you unable to read and unable to work, you may qualify for benefits. But it's the impairment, not the illiteracy, that would qualify you. Further, you can't get benefits from these programs unless you were already working; if illiteracy -- for whatever reason -- kept you from getting a job in the first place, state programs don't apply.
Social Security Disability
Social Security pays benefits to workers who become disabled, and these benefits can continue for life. But Social Security uses a strict medical definition of "disability," and illiteracy is unlikely to fit within it. Under this definition, you must have lost the ability to do work that you had previously done, and you must be unable to do other work because of your condition. In other words, the disability must be "total." You earn Social Security benefits by working, and again, if your illiteracy prevented you from working in the first place, you won't qualify.