The invention relates to a fluid reservoir (2) for an aerosol generator (50), the fluid reservoir (2) comprising a fluid chamber (4) for receiving a fluid (6), an opening (8) for guiding the fluid (6) received in the fluid chamber (4) outside the fluid chamber (4), and a collar portion (10) surrounding the opening (8) and extending into the fluid chamber (4). A first portion (12) of the fluid chamber (4) extends along the length of the collar portion (10) in a height direction (H) of the fluid chamber (4). A second portion (14) of the fluid chamber (4) is arranged adjacent to the first portion (12) in the height direction (H) of the fluid chamber (4). A lateral extension of the first portion (12) in the directions perpendicular to the height direction (H) of the fluid chamber (4) is smaller than a lateral extension of the second portion (14) in the directions perpendicular to the height direction (H) of the fluid chamber (4). Further, the invention relates to a fluid reservoir (2') for an aerosol generator (50), the fluid reservoir (2') comprising a fluid chamber (4') for receiving a fluid (6'), an opening (8') for guiding the fluid (6') received in the fluid chamber (4') outside the fluid chamber (4'), a recess (9) arranged at least partly below the opening (8') in a height direction (H) of the fluid chamber (4'), and a cover member (30') which releasably or permanently seals the recess (9). Moreover, the invention relates to an aerosol generator (50) comprising the fluid reservoir (2, 2').
