plutocracy (n.)

"government by the wealthy class; a class ruling by virtue of wealth," 1650s, from Greek ploutokratia "rule or power of the wealthy or of wealth," from ploutos "wealth" (see Pluto) + -kratia "rule" (see -cracy). Synonym plutarchy is slightly older (1640s). Pluto-democracy "plutocracy masquerading as democracy" is from 1895.