Isaac Slater (1803 – 3 December 1883) was a British publisher of trade directories.
He was born in Manchester. In 1818 he became the apprentice of James Pigot, a publisher of trade directories. Either in 1833, or after the death of Pigot's son in 1840, Pigot made Slater a partner in his firm, which was then called Pigot & Slater. Pigot died in 1843 and Slater then published directories in his own name.
Due to fierce competition from the firm of Kelly & Co., which in 1845 began expanding to other cities from its home market of London, Slater's company withdrew from the southern England market after 1852 and only published directories for Ireland, Scotland, and northern England.
After Slater's death, his company became a limited-liability company. A majority of its shares were acquired by Kelly & Co. in 1892, although the Kelly name did not appear on the newly acquired directories until years later (not until 1921 in Scotland).
- Richard Wright Procter (1880). Memorials of bygone Manchester: with glimpses of the environs. Manchester: Palmer and Howe.
- Pendred, John (1955). "Appendix H: General Directories". In Pollard, Graham. The Earliest Directory of the Book Trade (reprint of 1785 ed.). pp. 76–77,84. ISBN 0-19-721759-1.
- Slater's National Commercial Directory of Ireland; including ... English Towns of Manchester, Liverpool, Birmingham, West Bromwich, Leeds, Sheffield and Bristol, and in Scotland, those of Glasgow and Paisley. Manchester: I. Slater. 1846.
- Slater's Royal National and Commercial Directory and Topography of the Counties of Bedfordshire, Buckinghamshire, Cambridgeshire, Huntingdonshire, Norfolk, Oxfordshire, and Suffolk. London: Isaac Slater. 1850.
- Slater's Royal National and Commercial Directory and Topography of the Counties of Bedfordshire, Berkshire, Buckinghamshire, Cambridgeshire, Hampshire, Huntingdonshire, Lincolnshire, Norfolk, Oxfordshire, and Suffolk. Manchester: Isaac Slater. 1852.
- Southport & Birkdale, 1883