Adeline Jay Geo-Karis (March 29, 1918 – February 10, 2008) was a Republican politician and a member of the Illinois Senate for the 31st District, where she served for over 25 years.^[1] Prior to her election as Senator, she was in the Illinois House of Representatives from 1973 to 1979.^[1] Known simply as "Geo" to her constituents, she was a popular politician in Lake County, Illinois for many years.^[2] Known for her no-nonsense attitude and her ability to work across party lines,^[2] she also served for a time as Mayor of Zion.

Born in Greece,^[1] Geo-Karis came to America at the age of four with her parents.^[2] She attended Northwestern University and the DePaul University College of Law.^[1] She rose to the rank Lt. Commander in the United States Naval Reserves before retiring with a top secret security clearance.^[1] She also served as a Justice of the Peace and later as an assistant state's attorney in Lake County.^[1]

Due to an inter-party feud which included Republican Susan Simpson challenging Geo-Karis after she had told her she wanted to stay on for one more term, Geo-Karis endorsed Democrat Michael Bond to replace her.^[3] Bond's election, in a historically Republican district, was one of the many Democratic victories in 2006 that gave the Democratic Party a super-majority in the State Senate. Geo-Karis finished her final term in the 94th General Assembly where she served as the Executive Appointments Co-Chairperson. She also served on the Senate Committee of the Whole and the Pensions & Investments committees.^[1] Geo-Karis was also an avid supporter of Saint Demitrios Greek Orthodox Church, and was a member there for over fifty years.

She died on February 10, 2008, aged 89, of natural causes, at Glenbrook Hospital in Glenview, Illinois.^[4] The Adeline Jay Geo-Karis Illinois Beach State Park in Zion is named for her.^[5]