Ryan will join the firm on 13 November from Irish Life Investment Management, where she worked as head of responsible investment. She was also chair of the CDP Ireland Network, launched the 30% Investor Initiative Ireland and contributed to Ireland's Climate Action Plan.
Previously, Ryan founded an ESG investment research and analytics firm, Global Green Investments, which advised clients including the World Bank, the European Commission and the UK Government.
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Kathryn McLeland, CFO of M&G, said: "I am delighted to welcome Kathy to M&G. The depth of her technical expertise and wealth of experience progressing sustainable investing makes her ideal to drive our sustainability strategy forward."
Ryan added: "Our industry has an immense role to play in improving sustainable outcomes achieved and financing the transition to net zero. Through responsible asset management, pensions, life and savings, M&G can play a significant role in developing sustainable long term investment solutions and building on existing initiatives such as PruFund Planet and its Catalyst investment strategy.
"I look forward to working with my colleagues to build on M&G's existing capabilities and progress its approach to sustainability."