BOSTON, Nov 30 (Reuters) - Hedge fund manager David Einhorn has lost 20.6 percent this year, widening already deep losses when a bet on SunEdison cratered more than 50 percent this month, two people who have seen his returns said on Monday.

Einhorn's Greenlight Capital lost 5 percent in November, the people said. The Standard & Poor's 500 stock index gained 1.17 percent during the month.

Einhorn blamed much of the month's decline on SunEdison and thanked investors for supporting the New York-based hedge fund during a difficult year, in a brief note sent to investors on Monday evening, the sources said.

(Reporting by Svea Herbst-Bayliss; Editing by Sandra Maler)