TWSI may refer to:

• Two-wire serial interface, a type of I²C
• Tottenham War Services Institute, a charity in London
• Tactile Walking Surface Indicators

• Catarman, Northern Samar
• Cat Arm Hydroelectric Development
• Cat Arm Reservoir
• Catarr
• Catarrh
• Catarrhal Noise
• Catarrhine
• Catarrhini
• Catasauqua (PA)
• Catasauqua, PA
• Catasauqua, Pennsylvania
• Catasetum
• Catasterism
• Catasterismi
• Catastrophe
• Catastrophe film
• Catastrophe films
• Catastrophe modeling
• Catastrophe Modeling
• Catastrophe movie
• Catastrophe (play)
• Catastrophes
• Catastrophe theory
• Catastrophic
• Catastrophic failure