馬偕牧師1844年3月21日出生於加拿大安大略省牛津郡的左拉村（Zorra Township, Oxford County, Ontario, Canada），他的父親（名字也叫做 George Mackay）和母親都是虔誠的基督徒，1830年代從蘇格蘭移民到加拿大務農維生。馬偕是家中最小的兒子，上面有三個哥哥、二個姊姊。由於出生在虔誠的長老會基督徒家庭中，受到父母的薰陶，馬偕從小的願望就是當傳教士。
George L. Mackay was born on March 21, 1884 in Zorra Township near Woodstock, Oxford County, 100 miles west of Toronto, Canada. Mackay‘s father (also named George) and mother migrated from Scotland to Canada in the 1830s. Mackay was the youngest of six children, with three brothers and two sisters. Coming from a Calvinistic Presbyterian background, Mackay inherited from his parents a strong work ethic. Most importantly, he had faith in Christ and thought of becoming a missionary in his youth.