Single Immigration Desk
Plain English
It's a one-stop immigration desk that sits inside every Prefettura. It coordinates the paperwork between employers, families, the Questura, and Italian consulates abroad. Almost all work-based hires from outside the EU and all family-reunification cases pass through here.
Why it matters
It's the office that issues the work nulla osta when Decreto Flussi quotas open, and the family nulla osta for reunification. It also runs the integration agreement (Accordo di Integrazione) signing for new residents.
Real example
"Once Daniela's work nulla osta was approved, the SUI at the Prefettura di Roma called her in to sign her employment contract together with her new employer. Only then was her residence permit released."
Common confusion
Don't go to the SUI to renew your permesso. That goes through the post office kit and the Questura. The SUI mainly deals with the entry stage of work and family cases.
Official source
Ministero dell'Interno (Sportello Unico per l'Immigrazione)