| State: | PR |
| Type: | PR |
| Route: | 821 |
| Length Km: | 6.0 |
| Established: | 1953 |
| Direction A: | South |
| Terminus A: | in Corozal barrio-pueblo |
| Junction: | in Corozal barrio-pueblo–Pueblo |
| Direction B: | North |
| Terminus B: | in Abras |
| Municipalities: | Corozal |
| Previous Type: | Ter |
| Previous Route: | 820 |
| Next Type: | Ter |
| Next Route: | 823 |
Puerto Rico Highway 821 (PR-821) is a north–south road located in the municipality of Corozal in Puerto Rico. With a length of 6km (04miles), it begins at its intersection with PR-891 between downtown Corozal and Barrio Pueblo, passing through Abras barrio until its terminus at PR-630 near Mavilla barrio of Vega Alta municipality.
This highway consists of one lane in each direction for most of its length, except in the southern terminus, where Calle San Ramón is a one-way street with a single lane from Calle Colón to PR-891. After that, PR-821 heads to the north, meeting with PR-159 on its way to Abras. Between Barrio Pueblo and Abras, PR-821 becomes rural, connecting several neighborhoods and sectors until its transition to PR-630 near the Vega Alta municipal limit.
Prior to its numerical designation, PR-821 was only known as Spanish; Castilian: Camino del Abra. The current numerical designation corresponds to the 1953 Puerto Rico highway renumbering, a process implemented by the Puerto Rico Department of Transportation and Public Works (Spanish; Castilian: Departamento de Transportación y Obras Públicas) that increased the insular highway network to connect existing routes with different locations around Puerto Rico.