Don't Knock Twice may refer to:

• Don't Knock Twice (film), a supernatural horror film directed by Caradog W. James
• Don't Knock Twice (video game), a horror video game developed by Wales Interactive

• Samarium-Cobalt
• Samarium-Cobalt magnet
• Samarium(III) chloride
• Samarium (III) chloride
• Samarium(II) iodide
• Samarium (II) iodide
• Samarium trichloride
• Samarium–cobalt magnet
• Samariá Gorge
• Samarkan
• Samarkand
• Samarkand Sulci
• Samar (province)
• Samar Province
• Samarqand
• Samarqand Region
• Samarqand Wiloyati
• Samarra'
• Samarra
• Samar Sen
• Samarskaya Oblast', Russia
• Samarskite-(Y)
• Samartha Bharat
• Samarth Ramdas
• Samarth Ramdas Swamy