Obaid Siddiqi (1932–2013) was a pivotal figure in establishing modern molecular biology in India. His contributions started with fungal genetics, including the discovery of polarised ‘negative interference,’ then bacterial genetics, where he elucidated fundamental mechanisms of genetic suppression, DNA transfer, and conjugation. His research shift to Drosophila neurobiology was marked by collaborations with Seymour Benzer and Veronica Rodrigues, leading to insights into synaptic physiology and chemosensory pathways. Beyond his research, Siddiqi played a visionary role as an institution-builder, notably in founding the Molecular Biology Unit (MBU) at the Tata Institute of Fundamental Research (TIFR) and establishing the National Centre for Biological Sciences (NCBS) of TIFR. His mentorship philosophy, characterised by intellectual rigour, freedom, and personal care, cultivated generations of scientists. Siddiqi stands out as a figure whose approach to science and commitment to nurturing excellence had a national and global impact.