Valerie Susan Isham (born 1947) is a British applied probabilist and President of the Royal Statistical Society 2011–12.
Isham's research interests in include point processes, spatial processes, spatio-temporal processes and population processes. She went to Imperial College London (B.Sc., Ph.D.) where she was a student of a prominent statistician David Cox. She has been a professor of probability and statistics at University College London since 1992. She was the president of the Royal Statistical Society for 2011–2012. She was awarded its Guy Medal in Bronze in 1990.