An ICP (Ideal Customer Profile) is the specific company or person archetype your product fits best — the buyer who gets the most value, the easiest sales conversation, and the lowest churn. ICP is different from buyer persona: persona is about who the buyer IS (their demographics, behaviour, motivations); ICP is about what makes them a fit (their company size, role, current stack, trigger).
A strong B2B ICP example: "Series A SaaS companies with 50-200 employees using HubSpot CRM who just hired their first VP Marketing." A weak ICP: "B2B SaaS founders." The first one makes every GTM decision faster; the second one tells you nothing actionable.
See the full ICP glossary entry for the framework.