Professor Thanu Padmanabhan contributed significantly to a broad spectrum of topics in astrophysics, cosmology, and classical and quantum aspects of gravitation. In his memory, the Editorial Board of General Relativity and Gravitation invited us to edit a Topical Collection "In Memory of Professor T Padmanabhan". This collection gives a snapshot of ongoing research in the subjects he worked on.Professor Thanu Padmanabhan (affectionately known as Paddy) was an internationally acclaimed Indian Theoretical Physicist and Cosmologist, who passed away on 17 September 2021. He was a guiding light for all his students and younger colleagues who interacted with him [1]. We had the good fortune of discussing various aspects of physics with Paddy on several occasions. The Editors of General Relativity and Gravitation (GRG) invited us to organise a Topical Collection "In Memory of Professor T Padmanabhan". We have put together this volume in his fond memory and invited contributions in subjects Paddy had worked on.