The 101st Illinois General Assembly convened on January 9, 2019, and adjourned sine die on January 13, 2021. Over that period, it was in session for a total of 99 days.

The 2018 elections for the Illinois Senate took place on November 6, 2018 to elect senators from 39 of the state's 59 Senate districts to serve in the 101st General Assembly, with seats apportioned among the states based on the 2010 United States census. Under the Illinois Constitution of 1970, senators are divided into three groups, each group having a two-year term at a different part of the decade between censuses, with the rest of the decade being taken up by two four-year terms. The Democratic Party has held a majority in the Senate since 2003, and gained a net of 3 seats.