William Henry Strayer (January 10, 1866 – October 18, 1946) was an American attorney and politician from the state of Oregon. He served in the Oregon State Senate from 1915 through 1946, representing Baker County. Throughout his long service as a state senator, he was part of a small minority of Democrats elected to the Oregon Senate. He was the only Democrat in the Oregon State Senate during the 1921 and 1931 legislative sessions. When he died in office, Strayer had served longer in the Oregon legislature than any other citizen in the state's history. Today, Strayer is the second-longest-serving legislator in Oregon history.