Liam O’Callaghan was born in Co. Limerick, Ireland, in 1946, shortly after the death of his veterinarian father, and shortly before the death of Liam’s sister Madeleine. Liam spent much of his early childhood in the care of his uncle Vincent, while his mother worked in London and Dublin. He survived two bouts with pneumonia, and one with tuberculosis, before the age of 4. Experience working at his family’s railway bar and dairy farm led Liam to apply himself keenly to the study of mathematics and physics at the (then all-boys) Christian Brothers School at Westland Row in Dublin. He received his BS Hons, MSc in Mathematics from University College Dublin in 1969 and then studied mathematics at Wesleyan University (Middletown, CT) on a Fulbright Fellowship, receiving his PhD in 1976. Liam’s life was forever changed by his time in graduate school. At Wesleyan, he met fellow mathematics PhD student Robin, whom he married in 1975. Furthermore, upon finding that in the US one could easily store a half-gallon of ice cream in the home freezer, Liam formed an intention to become a US citizen, a goal he realized in 1986. Liam and Robin lived for forty years on Battle Rd in Princeton, NJ, where they raised three boys and three girls. During his time in Princeton, Liam worked as a software engineer at RCA (later GE) Astrospace, and Telos (later Engility and L3 Communications), primarily working on orbit determination for communication satellites. He also received an MBA from Rutgers in 1983. Not long after attending their youngest daughter’s college graduation, Liam and Robin put their plans for a well-deserved rest on hold so Liam could help his oldest daughter raise her two young girls in Northern California. After four years of indulging his granddaughters’ every whim, Liam moved on to San Diego to spend time with his oldest son and his grandson. Finally, in 2017, Liam returned full-time to Princeton. Three more granddaughters soon arrived, to Liam and Robin’s delight. Liam and Robin entertained their grandbabies regularly, spoiled their irrepressible Boston Terrier, Spike, and also enjoyed travel to California, Ireland, and points on the East Coast. In late 2020, Liam received a diagnosis of Glioblastoma Multiforme, from which he died on January 2nd, 2022. In his last year, Liam often remarked with incredulity on his luck at meeting and marrying Robin; he said he could not have recruited a better partner with whom to share a life and raise a family. Being surrounded by his children and grandchildren was his greatest joy. His second greatest was recounting stories about his family’s achievements and notable characteristics, many of which are preserved in his series of comprehensive Christmas newsletters and thoughtful speeches at his children’s weddings. Liam is survived by his wife, Robin, his children, Liadan (Matt), Aindrais (Oksana), Lasair (Mike), Conall (Lucile), Ciaran, and Aishlinn (Ricky); his grandchildren, Evy, Didi, Vladimir, Céleste, Hélène, Birdie, and Mila; and one grandson expected in April. Liam’s family took him back to his birthplace of Effin, County Limerick, Ireland, where a Mass of Christian burial was celebrated on January 16. He was laid to rest in Ardpatrick Cemetery alongside generations of his family. A Mass will be said in Liam’s memory at 2pm on Saturday, March 12, 2022, at St. Paul Roman Catholic Church in Princeton, NJ. In lieu of flowers memorial donations may be made in Liam's memory to Wounded Warrior Project or the Tunnel to Towers Foundation.