HMS Neptune was a Leander-class light cruiser which served with the Royal Navy during World War II.

Built by Portsmouth Dockyard, Neptune was laid down on 24 September 1931, launched on 31 January 1933, and commissioned into the Royal Navy on 12 February 1934 with the pennant number 20.

During World War II, Neptune operated with a crew drawn predominantly from the New Zealand Division of the Royal Navy.

[3] In December 1939, several months after war was declared, Neptune was patrolling in the South Atlantic in pursuit of German surface raider heavy cruiser Admiral Graf Spee.

[7] Minutes later, Neptune's main guns scored three hits on the heavy cruiser Bolzano, inflicting some damage on her torpedo room, below the waterline and the "B" turret.

As a result, only one was still alive when their carley float was picked up five days later by the Italian torpedo boat Generale Achille Papa.