The Oklahoma Senate is the upper house of the two houses of the Legislature of Oklahoma, the other being the Oklahoma House of Representatives. The total number of senators is set at 48 by the Oklahoma Constitution.

Senators approve or reject gubernatorial appointments, and contribute to the creation of both state law and an annual state budget. Every ten years, they aid in drawing new boundaries for Oklahoma's electoral districts. The Oklahoma Senate also serves as a court of impeachment.

The presiding officer of the Senate is the lieutenant governor of Oklahoma, who is the president of the Senate. Since the 1960s, the president pro tempore of the Senate has presided over daily work. Prior to that time, the president of the Senate took a leading role in the Senate, including appointing committees and members to those committees. The president of the Senate may cast a vote only in the instance of a tie vote and may not vote to create a tie.

The 1907 Oklahoma Constitution established the Oklahoma Senate alongside the Oklahoma House of Representatives. It met in Guthrie, Oklahoma until 1910. Henry S. Johnston, the author of the initiative and referendum section of the Oklahoma Constitution, served as the first Senate President Pro Tempore.

After women in Oklahoma earned the right to vote in 1918, the Oklahoma Senate gained its first female state senator. Lamar Looney was elected in 1920 over a male incumbent, G. L. Wilson. Looney was a progressive Democrat and served from 1921 to 1929.

The United States Supreme Court "one man, one vote" decision in Baker v. Carr (1962) led to a court order that forced Oklahoma to equalize representation. Before that decision, Oklahoma had 48 senatorial districts that represented either a populous county or several less-populated counties, but did not provide for districts of equal population.

Since 1964, under the holding of Reynolds v. Sims, 377 U.S. 533 (1964) districts must be apportioned within a 5% margin of the average target size district as determined by the U.S. Census state population figures divided by the forty-eight districts. This allows for some districts to be slightly smaller or larger than others. The Oklahoma Senate draws its own maps of its district lines, which are subject to the approval of both the Oklahoma House of Representatives and the governor. Should the redistricting not occur in a timely manner, the lines are determined by a panel of five statewide elected officials.

In 1966, voters approved 90-day legislative sessions and, in 1968, they voted to create a Board of Legislative Compensation.