Jillian Ooi is a geographer and seagrass ecologist, and an Associate Professor in the Department of Geography, Universiti Malaya. She is currently Deputy Dean (Research & Innovation) at the Faculty of Arts and Social Sciences. Seagrass meadows shelter young fish, feed dugongs and turtles, and store carbon, yet they are easily overlooked beside coral reefs, a problem known as "seagrass blindness" that she has spent two decades challenging.

Jillian produced the first maps of subtidal seagrass meadows in Malaysia. Her research asks what makes a suitable habitat for seagrass, how meadows support fish and dugongs, and how damaged meadows can be restored with local communities. She currently leads a Johor-wide seagrass mapping programme funded by Yayasan PETRONAS and is studying the hidden root systems that hold meadows together.

Her work has shaped marine protection in Malaysia. In 2005 she was part of the four-person team that carried out Malaysia's first large-scale dugong survey, which confirmed dugong herds in Johor and prompted the state government to propose a dugong sanctuary. The eastern Johor islands were later recognised by the IUCN as part of the Mersing Archipelago Important Marine Mammal Area (2019). Her seagrass findings helped persuade the government to reject a proposed airport on protected reef and seagrass habitat at Tioman Island (2007). She also led the seagrass assessment that informed the creation of Kepulauan Lima Marine Park, gazetted in 2023.

Beyond policy, she trains local communities and corporate volunteers to monitor seagrass in the Sungai Johor and Sungai Pulai estuaries and in Mersing. She brings seagrass to new audiences through the arts as well. Her gamelan theatre production Seruan Setu (2023) played six sold-out performances at the Kuala Lumpur Performing Arts Centre, and she has spoken about it at the World Seagrass Conference and at COP28.

Jillian holds a PhD in Seagrass Biogeography from the University of Western Australia and came to marine science from environmental social science. In 2022 she was named one of six Pew Fellows in Marine Conservation worldwide, and she sits on the Steering Committee of the World Seagrass Association.

When she is not underwater watching grass grow, Jillian is Artistic and Music Director of Rhythm in Bronze, a contemporary gamelan ensemble in Kuala Lumpur. Her compositions and music direction have won BOH Cameronian Arts Awards, including Best Original Composition and Best Music Director. The sea remains her greatest source of musical inspiration.