Thomas Brennan Gillis Sr.

Thomas B. Gillis Sr., of Sanibel Island, FL and South Chatham, MA, a devoted family man, proud U.S. Navy veteran, and longtime Raytheon executive, died peacefully at his home on August 9, 2025. He was 97.

Born in Jamaica Plain, Boston, Massachusetts, to Catherine (Brennan) Gillis and John Angus Gillis, Tom graduated from Northeastern University, School of Engineering and began his life's work at Raytheon as a co-op student. Over a distinguished career of 40 years, he rose to executive leadership, known for his integrity, calm judgment, and generous mentorship. He was a charter member of the International Society of Hybrid Microelectronics.

Tom lived in Dover and Chatham, Massachusetts, and later on Sanibel Island, Florida. His family's roots on Cape Cod run a century deep-one hundred years on the same piece of land in South Chatham. He spent countless summers there: first as a boy, then with his children, and later with his grandchildren, sharing long days on the water and fun evenings at the Band Concert. He was the one with the toolbox-often on a ladder patching shingles or in his basement workshop -well into his later years.

An avid outdoorsman, he embraced every season-skiing in winter and boating in summer. For many years he delighted in taking his children to ski races and cheering them on from the sidelines, building family memories. He took great joy in sailing the waters around Nantucket Sound and beaching on Monomoy. A lifelong mariner, he was commander of the Sanibel-Captiva Sail & Power Squadron, taught the Florida Safe Boating Class, and logged countless happy miles aboard his boat, The Water Music.

He was preceded in death by his beloved wife, Elizabeth "Beth" (Flanagan) Gillis d. 2022, and by his youngest son, Colin William Gillis, d. 2023 (Louise) of Harwich, also his brothers John Angus Gillis d. 1959 and Colin William Gillis d. 1993.

Tom is survived by his children: Elizabeth Warden (the late William, 2024) of Newport Coast, CA; Catherine Kjeell (Bille) of San Clemente, CA; and Christina Gillis Stevens (Howard Belger) of South Chatham, MA; Thomas B. Gillis, Jr. (Arabella) of Los Altos, CA; and by 13 grandchildren and many nieces and nephews who will miss their Grampy's steady encouragement and support of their successes in life. He is also remembered with love by his close-knit extended family including his late brother John's children: Jack Gillis (Marilyn) of Chevy Chase, MD, Jean Gillis of South Chatham. MA and Elizabeth Kennard (Spencer) of South Chatham, MA.

Tom will be remembered by his Florida friends and neighbors for his unwavering commitment to those he loved, especially his wife. He could be seen daily walking her around the island and faithfully tending his garden.

According to his wishes, the family requests that his friends and acquaintances perform a small act of kindness to someone in need or donate to the Clinic for the Rehabilitation of Wildlife on Sanibel Island (www.crowclinic.org).

A service will be held on Saturday Sept 6th at 10:00 AM at Holy Redeemer Church, at 57 Highland Ave, Chatham with a reception following on Gillis Road in South Chatham.

"Fair winds and following seas."