"Humanitarian space" refers to an operational environment that allows humanitarian actors to deliver humanitarian aid according to humanitarian principles and in line with international humanitarian law. The paper reviews how the Gaza Strip exemplifies the decline of humanitarian space under a prolonged siege. It is divided into three sections. First, it examines the concept of the humanitarian space. Second, it highlights the main features of the siege and analyses the magnitude of the humanitarian crisis experienced by Gaza Strip over the last 12 years in various fields. The third section discusses the factors led to the shrinking of the humanitarian space in the besieged Gaza Strip. "Humanitarian space" refers to an operational environment that allows humanitarian actors to deliver humanitarian aid according to humanitarian principles and in line with international humanitarian law. The paper reviews how the Gaza Strip exemplifies the decline of humanitarian space under a prolonged siege.