A fluid delivery device (1) for discharging a fluid comprises a housing (2, 3), piston pump (4), biasing mechanism (5, 101), and trigger mechanism (6); the housing (2, 3) comprising a basal end (3) and discharge end (2) having an outlet (10) for discharging the fluid; the piston pump (4) comprising a casing (20) defining a pump chamber (35) for fluid storage, piston (21) slidably movable relative to the pump chamber (35), piston plunger (22), and delivery channel (59) for delivering fluid discharged from pump chamber (35) to outlet (10); the trigger mechanism (6) being movable from cocked configuration, preventing transfer of biasing mechanism (5, 101) force to the casing (20) to prevent casing (20) movement towards the outlet (10), to triggered configuration, enabling transfer of biasing mechanism (5, 101) force to the casing (20) to cause casing (20) movement towards the outlet (10) to discharge fluid from the pump chamber (35). The biasing mechanism (5, 101) comprises one or more flexible catch members (104) which in cocked configuration are catched and in triggered configuration are decoupled from the housing (2, 3). The trigger mechanism (6) comprises a manually movable button (100) at the housing basal end (3) comprising an obstructer (114) that in cocked configuration engages the catch members (104) to prevent decoupling.