Haig was born in Bala Cynwyd, Pennsylvania, the middle of three children of Alexander Meigs Haig Sr., a Republican lawyer of Scottish descent, and his wife, Regina Anne (née Murphy). When Haig was 9, his father, aged 41, died of cancer. His Irish American mother raised her children in the Catholic faith. Haig initially attended Saint Joseph's Preparatory School in Philadelphia, Pennsylvania, on scholarship; when it was withdrawn due to poor academic performance, he transferred to Lower Merion High School in Ardmore, Pennsylvania, from which he graduated in 1942.