The 9th congressional district of Illinois covers parts of Cook, Lake, and McHenry counties as of the 2021 redistricting which followed the 2020 census.

It includes all or parts of Chicago, Evanston, Glenview, Skokie, Morton Grove, Niles, Northfield, Prospect Heights, Wilmette, Buffalo Grove, Hawthorn Woods, Wauconda, Island Lake, Long Grove, Lake Barrington, Algonquin Township, Cary, Crystal Lake, Lake in the Hills, Lakewood, Oakwood Hills, Trout Valley, Algonquin, Port Barrington, Barrington Hills, and Fox River Grove.

The 9th district takes in the Chicago neighborhoods of Rogers Park, Edgewater, and West Ridge; most of Uptown; and part of Lincoln Square.

Outside of the Chicago city limits, the district takes in the Cook County communities of Evanston, Glenview, Skokie, Morton Grove, Niles, Lincolnwood, and Golf; most of Northfield and Prospect Heights; northeastern Park Ridge and Arlington Heights; western Northfield and Buffalo Grove (shared with Lake County); southeastern Northbrook; northern Mount Prospect; half of Wilmette south of Lake Ave; most of Prospect Heights; and part of Glencoe, Des Plaines, and Wheeling (shared with Lake County).

The 9th and 5th districts are partitioned by partitioned by the Fox River, Kelsey Rd, W Miller Rd, Echo Lake Rd, Sacomano Meadows Pond 1, Midlothian Rd, N Old Henry Rd, N Quentin Rd, Lake Zurich Rd, Twin Orchard Country Club, Mundelein Rd, Hicks Rd, Bridgewater Farm, Crossing Pond Park, and Arlington Heights Rd.