Lionel Herbert Dahmer (/ˈdɑːmər/; July 29, 1936 – December 5, 2023) was an American research chemist, author, and father of serial killer Jeffrey Dahmer.In 1994, he wrote A Father's Story, a non-fictional account on his son Jeffrey's upbringing, subsequent progress to become a world-wide-known serial killer and its aftermath.[3] Lionel's figure has been controversial in the subsequent years since his son's crimes, as both he and his first wife were accused of neglecting Jeffrey during his childhood.[citation needed]

Lionel Herbert Dahmer was born in West Allis, Wisconsin, on July 29, 1936, to Herbert Walter Dahmer, a high-school math teacher and barber, whom Dahmer described as "a good father, as caring and concerned as any child would wish, and Catherine Jemima Hughes, an elementary school history teacher. 

Dahmer received his primary education and secondary education at local Wisconsin schools and enjoyed a relatively good childhood.

Dahmer enrolled in the University of Wisconsin–Madison in 1954 and obtained his BS in chemistry in 1959. Dahmer married later that year, on August 22,[5] to a 23-year-old teletype instructor called Joyce Annette Flint (1936–2000). In A Father's Story, Dahmer related that, from the very beginning, their marriage struggled due to Joyce's poor mental health and irascible and tempestuous behavior and his own inability to fully keep up with it. Shortly after Joyce got pregnant, she began to suffer seizure episodes, apparently from their neighbor's kitchen's foul odors, which caused them to move out to Dahmer's parents' home, shortly before their firstborn's delivery in early 1960, to receive attention from his parents. During the latter months of the pregnancy, Joyce suffered from increased mental breakdowns and seizures, which, according to her doctor "were rooted in Joyce's mental, rather than physical state" and which aggravated her already severe prescription barbiturates and morphine addiction, to the point of taking as "many as twenty-six pills a day" and being constantly sedated to ease her pain. Decades after, he reflected about the long-lasting and eventual terminal effect in his marriage:

In any event, we never really came to terms with the conflicts of that first year. Because of that, I think that this first troubled experience laid the foundation for a longer, and even more troubled, marriage. In some sense, our relationship never recovered from the damage done to it at this early stage, never really improved.

During the early years of Jeffrey's life, Dahmer's academic responsibilities and, later on, long work shifts prevented him from spending enough time with his wife and children. Shortly after Jeffrey's birth, Dahmer received a Master of Science degree from Marquette University in 1962 Later, he enrolled at Iowa State University, where he earned a Doctor of Philosophy degree in October 1966.[8] He described himself as average, even considered himself a mediocre student:

I was never a great student. What others got quickly, took me much longer. I was a plodder, a plugger, a hard worker. For me, anything less than an all-out effort would mean failure. Others had flashes of creative brilliance, of sudden illumination, but I had only the power of my own will.

In 2020, Dahmer appeared in Jeffrey Dahmer: Mind of a Monster.[9] In 2022, Dahmer considered suing Netflix over the series Dahmer – Monster: The Jeffrey Dahmer Story.

Dahmer lived in Seville, Ohio, in his later years. His second wife, Shari, died in January 2023, and he died from a heart attack eleven months later, at a hospice in Medina, Ohio, on December 5, at the age of 87.

Dahmer, Lionel Herbert (1994). A Father's Story. William and Morrow Company Inc. ISBN 978-0688121563.

Masters, Brian (2020). The Shrine of Jeffrey Dahmer. Hodder & Stoughton.