Sir Gilbert Thomas Walker CSI FRS (14 June 1868 – 4 November 1958) was an English physicist and statistician of the 20th century.

Walker studied mathematics and applied it to a variety of fields including aerodynamics, electromagnetism and the analysis of time-series data before taking up a teaching position at the University of Cambridge.

His hard studies led to ill-health and he spent several winters recuperating in Switzerland where he learnt skating and became quite expert.

A growing interest in the work of Lockyer on cycles led him to choose a mathematically inclined successor who would be Walker, despite his lack of experience in meteorology.

Walker was an established applied mathematician at the University of Cambridge and gave up a Fellowship at Trinity to take up a position as assistant to the meteorological reporter in 1903.

[4] [7] Walker developed Blanford's idea with quantitative rigour and came up with correlation measures (with a lag) and regression equations (in time-series terminology, autoregression).

[8] The methods he introduced for time-series regression are now partly named after him (the other contributor was Udny Yule who studied sun-spot cycles) as the Yule-Walker equations.

[16] Walker continued his studies of yearly weather and climate change even after his retirement from India (in 1924 when he was knighted) and acceptance of a professorship in meteorology at Imperial College London.

[21] Walker's interest in a wide range of subjects made him note the growing insularity of specialists:[22] There is, to-day, always a risk that specialists in two subjects, using languages full of words that are unintelligible without study, will grow up not only, without knowledge of each other's work, but also will ignore the problems which require mutual assistance.Walker married Mary Constance Carter in 1908 and they had a son, Michael Ashley, and a daughter, Verity Micheline.