A Shabbos goy, Shabbat goy or Shabbes goy (Yiddish: שבת גוי, shabbos goy Modern Hebrew: גוי של שבת goy shel shabat) is a non-Jew who performs certain types of work (melakha) which Jewish religious law (halakha) enjoins the Jew from doing on the Sabbath. The phrase is a combination of the word "Shabbos" (שבת) meaning the Sabbath, and goy, which literally means "a nation" but colloquially means a "non-Jew" (in Biblical Hebrew "goy" means simply "a nation", but in Mishnaic Hebrew it is used in the sense of "a non-national", i.e., "a non-Jew"). The word goy is often seen as pejorative term for non-Jews.
Judaism prohibits Jews from doing certain types of work, known as melakha, on the Sabbath. Within certain guidelines (see Shulkhan Arukh), a non-Jew may perform certain acts which are beneficial to Jews but which may not be performed by Jews on the Sabbath. There are numerous restrictions and certain types of work are prohibited, such as contractor work.
A "shabbat goy" is not needed where life is at stake (pikuach nefesh). Jewish physicians must work on the Sabbath if their work is needed to save lives.
Examples
In the 20th century, Colin Powell, Mario Cuomo, Martin Scorsese, Floyd B. Olson, Harry Truman, and the adolescent Elvis Presley assisted their Jewish neighbors in this way.