The water company has climbed nine places to claim second spot during the last quarter, as part of the Tortoise Responsibility100 Index.
The index examines how much FTSE 100 companies are doing to ensure a safe, fair and sustainable world, ranking them on their ability to do what they say they would.
This recognition follows a sustainability report recently published by Severn Trent, highlighting how its environmental, social and governance commitments are embedded in its business plan and what its ambitions are for the future.
Severn Trent chief executive Liv Garfield said: “I’m incredibly proud that we’ve been ranked second in the FTSE 100 for our environmental, social and ethical performance over the last quarter.
“Being socially responsible is at the very heart of our business plan, as we outlined in our first ever Sustainability Report, published only recently.
“It’s great to get this recognition, which will only spur us on to do more for the environment, our customers and the communities we serve.”
The ranking uses measures that deliver on the UN Sustainable Development Goals, with each company’s score calculated from publicly available data across more than 200 sources.
Scores comprise 17 individual targets spanning a wide range of topics from poverty and inequality to climate change and biodiversity.