The Peninsula Observer was an underground newspaper published in Palo Alto, California from July 7, 1967, to November 1969.

Co-founded by Barry Greenberg and David Ransom, it was produced by Stanford undergraduate and graduate students opposed to the war in Vietnam, with community members and others.

Early issues were published as the Midpeninsula Observer.

Editorship rotated among a group including Greenberg and Ransom, Randy Bonner, Marlene Charyn, Peter Dollinger, David Shen, Maureen Kulbaitis, and Joanne Wallace.

Published roughly biweekly for two years, it printed its last issue in November 1969.