Holbrook is a hamlet and census-designated place (CDP) within the Towns of Brookhaven and Islip, in Suffolk County, New York, United States.

The oldest still standing building from this period is St. John's Lutheran Church, which was built in 1863.

In 1875, the Nevins and Griswold cigar factory operated at the original LIRR station.

[2][4] It also was the center of growth as Long Island MacArthur Airport developed along the community's western border.

[5] According to the United States Census Bureau, the CDP has a total area of 7.2 square miles (18.6 km2), all land.

[4][5] All of Holbrook is within the Sachem Central School District, which is independent of town borders.

[5] Residents living in the north and west parts of the hamlet go to Sachem High School North in Lake Ronkonkoma, while those living in the south and east parts of the hamlet go to Sachem High School East in Farmingville.

[5][13] Holbrook is accessible on the Ronkonkoma Branch of the Long Island Rail Road.