No, but you must respect the formality.

• The Translation: "The Groom is wearing a Tuxedo. We would love for you to wear one too, but we don't want to force you to rent one."
• The Safe Bet: If you don't own a Dinner Suit, wear a Black, Charcoal, or Midnight Blue lounge suit. Wear a white shirt and a conservative dark tie.
• The Don't: Do not wear a light grey suit, beige chinos, or a loud patterned shirt. Do not wear a bow tie with a normal suit—it looks like a costume. If not in a Tuxedo, wear a long tie.