Stephanopoulos, who last month began his new job co-anchoring ABC's "Good Morning America," had been doing double duty the past several weeks.
Wrapping up his final "This Week" broadcast Sunday, he thanked the audience as well as his colleagues.
ABC has said no replacement will be named right away, with a rotating group of substitutes filling in.
The next two weeks, ABC correspondents Jake Tapper and Terry Moran (mor-AN') are scheduled to host. Both are considered candidates to land the job permanently, as is PBS' Gwen Ifill. The name of Ted Koppel, original anchor of ABC's "Nightline," surfaced last week as another possible candidate.