Businesses
- T Henshaw and Company Limited
- Technical School
- Tedcastle McCormick and Company Limited
- Telegraph and Telephone Journal
- Telegraph Works Company Limited
- Terenure Laundry Company Limited
- Terminus Hotel
- The Advertising Company Limited
- The American Bar
- The Athletic Club
- The Cigar Stall
- The College Studios
- The Oval, public house
- The University Press
- Thomas Adams Limited
- Thomas Cook and Son
- Thomas Dockrell Sons and Company Limited
- Thomas F Burke
- Thomas Heiton and Company Limited
- Thomas Henshaw and Company Limited
- Thomas J Costello and Son
- Thomas Lenehan and Company
- Thomas Lyons and Company, clothing manufacturer
- Thomas Neary, restaurant and caterer
- Thomas R O'Beirne, family grocer
- Thomas R Scott and Company, cabinet makers
- Thomas Read and Company, cutlers
- Thomas Rigby and Sons Limited
- Thomas Smith
- Thomas Tapling and Company Limited
- Thomas W Begge and Company Limited
- Thompson and Company
- Thompson's Motor Car Company Limited
- Tivoli Theatre Company
- Todd Burns and Company Limited
- Tower Bar
- TP Eckfor and Company Limited
- Tramway Depot
- Traynor Brothers
- Trinity College Dublin
- True Form Boot Company
- TT Mecredy and Son, solicitors
- Tuck and Company Limited
- Tullaroan Dairy and Creamery Company
- Turkish Baths Limited