The 41-year-old Scot, who retired from rowing after winning a medal at her fifth successive Games in Rio last year, will succeed Rod Carr as head of the funding agency for elite sport in Britain. Carr held the job for four years.
Grainger, who beat Paralympic swimmer Marc Woods to the post, has no previous experience of sports administration but is one of Britain's most respected athletes.
She takes over at a difficult time for UK Sport which was previously credited with transforming Britain's Olympic fortunes.
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British Cycling has been engulfed in controversy since it was accused of a culture of bullying and intimidation. Publication of an independent review into the allegations has been delayed.
(Reporting by Neil Robinson, editing by Ed Osmond)
