Placentia may refer to:

• Palace of Placentia, an English royal palace
• Placentia, Italy, a Roman city known today as Piacenza
• Placentia, Newfoundland and Labrador, Canada
  • Placentia Bay, body of water
• Placentia, California, United States
  • Placentia station, proposed train station in Placentia
• Battle of Placentia (disambiguation)
• Placentia Bay
• HMS Placentia, the name of two ships of the Royal Navy

• Placencia, Belize
• Plasencia, Extremadura, Spain
• Plentzia, Basque Country, Spain
• Piacenza (disambiguation)
• Plaisance (disambiguation), a French word
• Not to be confused with Placenta