Rev. Kenneth Theisen, O.S.B., a monk of Marmion Abbey, died on August 8, 2025, at St.
Patrick's Residence in Naperville, Il. Fr. Kenneth was born on November 1, 1941. Son of
Harry and Marie (Bohr) Theisen, he was the youngest of nine siblings, seven brothers
and two sisters. He attended Saint Theresa grade school in Aurora and graduated from
Marmion Military Academy in 1959. He attended one year of St. John Vianney
Seminary in Elkhorn, Nebraska and entered Marmion Abbey in July of 1960. After his
novitiate year, he was a student at St. Procopius College, graduating in 1964. He
professed solemn vows August 15, 1964. He spent two years studying theology at St.
Procopius Major Seminary. He took a year's leave of absence, serving as an instructor at
Marian Central Catholic High School in Woodstock, Illinois, 1966-67. In 1968 he
received a dispensation from his religious vows as a Benedictine monk. For the next ten
years he worked in Estes Park, Colorado, overseeing a motel and working with his
brother Richard in his roofing business.
After discernment, he decided to apply once again for entrance to Marmion Abbey. He
was invested as a novice in August of 1980. From 1981-1984, he did his theological
studies at Saint Meinrad School of Theology in Indiana. He professed solemn vows on
August 6, 1984, and was ordained to the priesthood on December 27, 1984.
Father Kenneth then entered a period of holding multiple roles at Marmion Abbey and
Marmion Academy. He began teaching assignments in the Mathematics Department of
the Academy. For three decades, he established himself as a master teacher and tutor in
Algebra and Advanced Math. He also served for several years as golf coach and as the
Dean of Men for the Resident Students.
At the Abbey, Fr. Kenneth served as Procurator and Prefect of the House, Kitchen
Master and Treasurer. He followed in the footsteps of his uncle, Rev. Luke Bohr, OSB,
serving as Prior of the monastery for ten years, and as keeper of Mass Intentions. Many
faithful in the parishes of the area benefited from the sacramental help provided by Fr.
Kenneth in his priestly duties, as well as in his role as a spiritual director. Fr. Kenneth
was an ardent Chicago Cubs fan, a person who never encountered a jigsaw puzzle he
could not finish. He was a loving family member to his numerous relatives, near and far.
In his last years, Father Kenneth experienced several debilitating physical ailments,
leading to a lack of mobility and confinement, first to the infirmary at the Abbey, and in
more recent years, to St. Patrick's Residence in Naperville, where he was deeply loved.
He maintained a keen mind, a firm faith, and sense of humor through it all.
Father Kenneth was preceded in death by his parents, two sisters (Doris and Sister
Merina, SSSF) and five of his brothers (Robert, Harry, Gerald, Ray and James). He is
survived by his brother Richard, many nieces and nephews, and his brother monks.

The body of Father Kenneth will be received at Marmion Abbey's St. Augustine of
Canterbury Church at 4:00 pm on Friday, August 15. Visitation will follow until 8:00
pm, with a Vigil Service at 7:00 pm. A Mass of Christian Burial will take place at
Marmion Abbey on Saturday, August 16, at 10:30 am. Visitation will continue the hour
before the start of the liturgy. Burial will follow at Marmion Abbey Cemetery.
Funeral arrangements were entrusted to The Daleiden Mortuary, 220 N. Lake St., Aurora, IL. 60506.
Please remember to sign the virtual guest book and leave condolences for Fr. Kenneth's family.