Firma U - Arendal
- Umwelt AS
- Uniqumboat AS
- Uveil AS
- Univa
- Unisub AS
- Uno Gigas AS
- Utdanningsforbundet Arendal
- Upstairs Arendal
- UFO Trafikkskole
- Umarin Sinsa
- Ugurean Gungor
- Umarin Sinsa
- Unge Lovende AS
- Ungdomskoret Ekko
- Ugland Skytterlag
- Unni Engebretsen Bryn
- Uab Csub LT
- Uno-X Arendal
- Uno-X Torsbudalen
- Univern Senter Arendal
- Unn Merete Fosse
- Uppstad økonomi og engros AS
- Utsyn familiebarnehage V/Berit Nordbø Aaneby
- Ufford Johanna Wilhelmina Quarles van