Electronic Journal of Differential Equations, Vol. 2023 (2023), No. 68, pp. 1-18. Title: Stability and instability of Kirchhoff plate equations with delay on the boundary control Authors: Haidar Badawi (Lebanese International Univ., Beirut, Lebanon) Mohammad Akil (INSA Hauts-de-France, France) Zayd Hajjej (King Saud Univ., Riyadh, Saudi Arabia) Abstract: In this article, we consider the Kirchhoff plate equation with delay terms on the boundary control. We give instability examples of systems for some choices of delays. Finally, we prove its well-posedness, strong stability, and exponential stability under a multiplier geometric control condition. Submitted April 18, 2023. Published October 16, 2023. Math Subject Classifications: 74K20, 47D60, 90C31, 93D15, 93D20, 35B35, 35B40, 93C80, 93C43. Key Words: Kirchhoff plate equation; boundary control; time delay; instability examples; strong stability; exponential stability.