Ranganathan Gregoire Yogeshwar (born 18 May 1959) is a Luxembourgish physicist and science journalist. He started gaining attention at the end of the 1980s in the German-speaking area for his science documentaries that were often coupled with critical analysis and prognoses of the societal effects of research in the natural sciences.
Yogeshwar grew up in Bangalore and Luxembourg and went to primary school in both places. His father is an Indian engineer and his mother a Luxembourgish art historian. He has a younger sister and a twin brother, Pierre Kalyana Yogeshwar, who is also a physicist. His grandfather was mathematician and librarian S. R. Ranganathan, the developer of the colon classification. Growing up, he spoke Luxembourgish, German, French, English, Tamil, Kannada, Hindi and Malayalam (the latter three to communicate with his housekeeper, teacher, and gardener, respectively).