The Romulans developed it, and the Klingons stole, it but are there any others who possess it either through theft or development?
In addition to the cultures mentioned, Memory Alpha mentions several others:
- The Federation (seen on the USS Defiant, Self-replicating mines and the Federation Holoship in Insurrection)
- The Terran Empire (seen on the ISS Enterprise)
- The Cardassian Obsidian Order (seen on the Koranak)
- The Kraylor (seen on the Nightingale)
- The Klingon-Cardassian Alliance (seen on the Regent's flagship
- The Remans (seen on the Scimitar)
- The Voth (seen on the Voth City Ship and the Voth research vessel)
- The Krenim Imperium (seen on the Krenim weapon ship)
- The Aldeans (seen on Aldea)
- The Sphere Builders (seen on the Delphic Expanse spheres)
- The Minosians (seen on Echo Papa 607)
- The Srivani (seen on Srivani vessels)
- The Hierarchy (seen on their ships)
- The Xyrillians (seen on their starships)
Bear in mind that this list does include some references to societies from other realities.
The Aldeans are a race of people who cloak their entire planet in When The Bough Breaks.
Suliban also have cloaking technology.
Quark managed to acquire a damaged cloaking device on the black market. He ultimately gave it to some Cardassians in Profit and Loss.
In Blaze of Glory, the Klingon empire supplied cloaking devices to the Maquis for use against Cardassia.