Ilchester is an unincorporated community and census-designated place in Howard County, Maryland, United States.

[8] The church used the Ellicott estate to start a college, initially called Mount Saint Clemens when it opened in 1868.

However, the current CDP extends southwest to include the suburban terrain of Howard County outside of the Patapsco River valley.

Maryland Route 100 is a freeway that runs through the southern part of Ilchester, serving the community at Exit 4 with Montgomery Road.

To the south, Route 100 intersects with Interstate 95, which forms the southeastern boundary of the Ilchester CDP.