John Barrett, chief executive of the Small Charities Coalition, will step down this summer.
Barrett, who has been at the SCC since its inception in 2007 and chief executive since 2014, will leave in July, according to a statement from the charity today.
He does not have a role to move on to but said he would spend the next few months considering his next step.
The SCC said it had begun the recruitment process for a new chief executive and hoped to have someone in place before Barrett departed.
Barrett became chief executive of the SCC after his predecessor Alex Swallow stepped down because his £45,000 salary was too large for the SCC’s tight finances.
Barrett said he was proud of his achievements at the SCC, particularly in dealing with its financial problems in the past three years.
According to its entry on the Charity Commission online register, the SCC had an income of £152,932 and expenditure of £124,666 in the year to 31 May 2015, compared with an income of £152,839 and spending of £158,696 in the previous year.
"I feel immensely honoured to have spent the formative years of my career at the Small Charities Coalition, helping to build it up from a humble idea into the significant and respected organisation that it is today," said Barrett in a statement.
"I am particularly proud of what the charity has achieved over the past three years, steering it through financial difficulties and setting it on course for a more sustainable future.
"It is within this context that I feel able to step down from SCC and pass the reins onto someone new, to take the charity through its next strategic review period and build on what we have all achieved. I remain chief executive until the end of July, during which time we will be launching some exciting new developments, including a revamped website and member portal."
Julia Kaufmann, chair of the SCC, said: "Since being appointed chair of the SCC last year I have worked closely with John and have been impressed by his commitment and depth of knowledge of the SCC and the sector.
"I am sorry that I will not be able to work with him for longer and wish John the very best for the future. We look forward to working with a new chief executive to build on the foundations John has worked so hard to create."