A prime contractor is any contractor that holds a direct contract with the project owner. The general contractor (GC) is the most common prime contractor on traditional design-bid-build projects. On projects with multiple primes (sometimes called "separate primes" or "multi-prime delivery"), the owner directly contracts with a GC plus separate primes for major specialty trades (mechanical, electrical, plumbing) instead of going through the GC.
Being a prime contractor carries direct contractual obligation to the owner, direct lien rights against the property, and direct exposure to owner-driven scope changes. Subcontractors do not have direct contractual relationship with the owner; they contract with a prime. The prime-vs-sub distinction matters for lien rights, payment flow, insurance requirements, and dispute resolution.