Ontario California ZIP Codes

Ontario holds 4 ZIP codes, all inside one county and one postal prefix.

We do not publish a delivery type (standard, PO box, unique) or a neighbourhood for each ZIP. USPS delivery-type products are licensed, and no clean-rights source maps ZIP codes to neighbourhoods — so the Ontario codes above are listed without a column we would have to invent.

Scope every ZIP code recorded for Ontario. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. ZIP codes are delivery-route groupings, not areas; the boundaries implied by any ZIP map are approximations.

Every Ontario ZIP code begins 917. Those first three digits identify the sectional center facility that processes mail for this part of California. Statewide that range covers 64 ZIP codes, so Ontario accounts for 6% of it.

Every California ZIP prefix and the region it covers →

ZIP codes and area codes are separate systems — one routes mail, the other routes calls — and they do not share boundaries. The codes below serve the same ground Ontario occupies.

• 840 Area code 840
• 909 Area code 909
• 951 Area code 951

Ontario California area codes in full →

Straight-line distance between place reference points, not driving distance.