Du Toit, Alexander Logie (1878-1948) was a South African geologist who helped form one of the foundations for the synthesis of continental drift theory and plate tectonics.

Du Toit was born on March 14, 1878, in Rondebosch, South Africa, near Cape Town. He received his early education from a local diocesan college. He graduated from South African College (now the University of Cape Town). He then spent two years studying mining engineering at the Royal Technical College in Glasgow. Next, he went to the Royal College of Sciences, London, to study geology. In 1901, Du Toit returned to the Royal Technical College, this time as a teacher. He also taught at the University of Glasgow. Du Toit went back to South Africa in 1903 and worked for the Geological Commission of Cape of Good Hope. He spent nearly the next two decades in the field mapping.

He later became chief geologist to the irrigation Department. He wrote several books during this time. In 1923, he received a grant from the Carnegie Institution, which allowed him to go to South America to compare the geology of the two continents. He described this work in A Geological Comparison of South America with South Africa. He found the continents alike in a number of ways, supporting Alfred Wegener's theory of continental drift, that the continents had once been joined. Then in his book, Our Wandering Continents (1937), he stated that they had at one time formed the supercontinent of Godwanaland, which was distinct from Laurasia the northern supercontinent. This view was not popular at the time, but it is now considered correct.

Du Toit served as a geologist consultant to the De Beers Consolidated Mines from 1927 to 1941. He was twice president of the Geological Society of South Africa.

Du Toit married Adelaide Walker while a student at the Royal Technical College. They had a son. Adelaide died in 1923. In 1925, Du Toit married Evelyn Harvey. He died on Feb. 25, 1948.