The Oregon State Senate is the upper house of the statewide legislature for the US state of Oregon. Along with the lower chamber Oregon House of Representatives it makes up the Oregon Legislative Assembly. There are 30 members of the state Senate, representing 30 districts across the state, each with a population of 141,242.^[2] The state Senate meets in the east wing of the Oregon State Capitol in Salem.

Oregon, along with Arizona, Maine, New Hampshire, and Wyoming, is one of the five U.S. states to not have the office of the lieutenant governor, a position which for most upper houses of state legislatures and for the United States Congress (with the vice president) is the head of the legislative body and holder of the casting vote in the event of a tie. Instead, a separate position of Senate president is in place, removed from the state executive branch. If the chamber is tied, legislators must devise their own methods of resolving the impasse. In the 72nd Oregon Legislative Assembly in 2003, for example, Oregon's state senators entered into a power sharing contract whereby Democratic senators nominated the Senate President while Republican senators chaired key committees.^[3]

Like certain other upper houses of state and territorial legislatures and the United States Senate, the state Senate can confirm or reject the governor's appointments to state departments, commissions, boards, and other state governmental agencies.

The current Senate president is Rob Wagner of Lake Oswego.^[4]

Oregon state senators serve four-year terms without term limits. In 2002, the Oregon Supreme Court struck down the decade-old Oregon Ballot Measure 3, that had restricted state senators to two terms (eight years) on procedural grounds.^[5]

According to the Oregon Constitution, two-thirds of senators are required to form a quorum. Republican senators have used this rule to block legislation by absenting themselves.^[6] In response to this practice, Oregon Ballot Measure 113 was passed in 2022 to disqualify members with ten unexcused absences from serving in the legislature following their current term. However, a Republican walkout went for six weeks during the 82nd Assembly in May and June 2023, the longest ever.^[7][8]

Kathryn Clarke was the first woman to serve in Oregon's Senate. Women became eligible to run for the Oregon state legislature in 1914 and later that year Clarke was appointed to fill a vacant seat in Douglas county by her cousin, governor Oswald West. Following some controversy concerning whether West had the authority to appoint someone to fill the vacancy, Clarke campaigned and was elected by voters in 1915.^[9] She took office five years before Nineteenth Amendment to the United States Constitution protected the right of all American women to vote.

In 1982, Mae Yih became the first Chinese-American elected to a state senate in the United States.

The 82nd Oregon Legislative Assembly, which holds its regular session from 2023 to 2025, has the following leadership:

Senate President: Rob Wagner (D-19 Lake Oswego)
President Pro Tempore: James Manning Jr. (D–7 Eugene)
Majority Leader: Kate Lieber (D-14 Beaverton)
Minority Leader: Tim Knopp (R-27 Bend)

• 2022 Oregon State Senate election