Isobel Armstrong FBA (born 1937) is a British academic. She is Emeritus Professor of English at Birkbeck, University of London and a Senior Research Fellow of the Institute of English Studies at the University of London. She is a Fellow of the British Academy.
She is a critic of nineteenth-century poetry, literature and women's writing. Her publications include The Radical Aesthetic (2000), Women's Poetry, Late Romantic to Late Victorian: Gender and Genre (1999) and Victorian Poetry: Poetry, Politics and Poetics (1993). She is also a published poet.
Possession: A Romance, the 1990 Booker Prize-winning novel by A. S. Byatt, was dedicated to Armstrong.
Armstrong is the younger sister of writer Diana Wynne Jones.