Cape and Islands state Sen. Dan Wolf announced this week that he will not seek a fourth term next year.

Mr. Wolf has represented the Cape and Islands since 2009.

In a statement released early Thursday morning, Mr. Wolf, a Democrat from Harwich, thanked his family, friends, employees, State House colleagues, and constituents.

“Serving as state senator from the Cape and Islands has been one of the greatest honors and experiences of my life,” he said in the statement, calling his decision not to run “the most difficult I’ve made.”

The senator did not give a reason for his decision. “For me, civic engagement includes elective office, but it encompasses much more,” the statement read. “I have learned this working with so many great people over the years. My commitment to continue this fight is as strong as ever; after next year, it will take new forms.”

Mr. Wolf is the co-founder and part owner of the regional airline Cape Air. His business interests in the airline led to a battle with the state ethics commission in 2013, shortly after he announced his candidacy for governor. The ethics commission ruled that because Cape Air had agreements with state agency MassPort to fly in and out of Logan Airport, Mr. Wolf was violating state ethics law.

Mr. Wolf permanently suspended his gubernatorial campaign and said he would resign his senate seat, but a later petition to the ethics commission led to new regulations that allow Mr. Wolf and others in his situation to hold elected office while having “financial interest in contracts that pre-date their election or appointment.”