1. Belgium

2. Canada

3. Ireland

4. Italy

5. Sweden

6. United Kingdom

7. United States

The following highways are numbered 666:

Belgium

• The pilgrimage centre of Banneux in Belgium is located on the N666 road.

Canada

• Alberta Highway 666
• Ontario Highway 666, renumbered to 658 in 1985

Ireland

• R666

Italy

• Strada regionale 666 di Sora (formerly strada statale 666 di Sora)

Sweden

• Länsväg 666, in Uppland, eastbound from Alunda.

United Kingdom

• A666 road

United States

• {{jct|country=USA|US|666|name1=former, renumbered in 2003 to {{jct|country=USA|US|491}}}}
• {{jct|state=FL|SR|666}}
• {{jct|state=OH|OH|666}}
• {{jct|state=PA|PA|666}}
• {{jct|state=TX|FM|666}}

• Ottorino Sartor
• Otto Ritschl (Theology)
• Otto Roehm
• Otto Roelen
• Otto Rohwedder
• Otto Rosenberg
• Otto Rossler
• Otto Rothstock
• Otto R. Skopil, Jr.
• Otto Ruff
• Otto Röhm
• Otto Rössler
• Otto Rühle
• Ottos
• Otto's
• Otto Sanchez
• Otto santi
• Otto's Brewery
• Otto Scavenius
• Otto Schaden
• Otto Scheff
• Otto Schenk
• Otto Scherzer
• Otto Schimek
• Otto Schlefenberg