A fuel cell stack assembly (101) comprising a fuel cell stack (102) comprising one or more fuel cells and a retaining member (100) comprising a first engaging region (104) that engages a first end face (110) of the fuel cell stack (102), a second engaging region (106) that engages a second opposing end face (112) of the fuel cell stack (102, and a joining region (108) configured to bias the first engaging region (104) towards the second engaging region (106). The retaining member (106) defines a fluid chamber (118) for communicating a fluid to or from the fuel cell stack (102).