Possibly.

Almost everybody agrees that a smallpox outbreak affected the Eora, whose territory encompassed what is now central Sydney and its southern suburbs, in around April 1789 (some, such as John Carmody, argue the outbreak was actually chickenpox, but this theory attracts very little support).

The outbreak was typically thought to have been accidentally spread by the First Fleet upon their arrival (samples of smallpox were carried with the fleet in their medical stores), though an alternative theory, advanced most recently by Campbell Macknight among others, posits that smallpox was actually introduced into Arnhem Land by Makassan trepang traders at some point in the 18th century, before spreading across the continent to the south-east.

Noel Butlin, writing in 1983, was the first in recent times to raise the possibility that smallpox could have been deliberately spread by the settlers at Sydney, and others have maintained this possibility since then. Supporters of this theory point to the precarious situation the white settlers faced at the time (food and ammunition shortages, the delay of resupply from England, increasing tensions in relations with Indigenous people, military forces spread thin guarding the expansion of settlement at Parramatta), the sudden emergence of the disease outside the normal season (late summer/early autumn instead of late winter/early spring), and the apparent point of origin being located well away from the settlement at Sydney (had the release been deliberate, this would have mitigated the risk of collateral damage to the white population). They also criticise the paucity of evidence for the Makassan theory, notably the lack of evidence of smallpox affecting communities along trade routes between Arnhem Land and the Sydney region. Michael Bennett and Chris Warren are among those who have most recently argued in favour of the deliberate release theory.

The evidence remains unsettled, but the deliberate release theory is at least plausible on the available evidence.