Tonelero (S21) was an Oberon-class submarine in the Brazilian Navy.

[1] The submarine was towed to Chatham Dockyard, where the 60-foot (18 m) central section was cut out and replaced.

[1] The fire was found to have originated in the cabling, and prompted the recabling of all under-construction Oberons.

[2] Tonelero was listed as active in the 1998-99 edition of Jane's Fighting Ships.

[2] On 26 December 2000 the Tonelero sank at her mooring in the Rio de Janeiro navy yards due to crew error.