Nigel Siederer, the Association of Charitable Foundations' first chief executive, is to stand down in order to "seek fresh challenges".
Siederer will leave at the end of June after 12 years at the helm of the association, which he helped transform from a small network of 50 trusts to a leading umbrella organisation for independent grant making.
It now represents 300 large and small grant making trusts, including Esmee Fairbairn, the Community Fund and Lloyds TSB Foundation.
The association will start advertising for a new chief executive in July, but in the interim deputy chief executive Bernie Morgan will take on the role.
Members of the association last week paid tribute to Siederer for helping to put it on the map and for pushing for reforms in charity investment law. Siederer started his career at the National Council for Civil Liberties, and helped set up the Federation of Independent Advice Centres during the 1980s.