The 1951 New Zealand waterfront dispute is the largest and most widespread industrial dispute in New Zealand history. Twenty thousand workers went on strike in support of the waterfront workers. Thousands more refused to handle "scab" goods. The dispute, sometimes referred to as the waterfront lockout or waterfront strike, lasted 151 days.

The distance of New Zealand and Australia from their traditional markets, meant that ports played a pivotal role in the economies of the countries. The waterfront inevitably became point of conflict between workers and their unions on one side, and capital (the employers) and the state on the other.

During the Second World War due to labour shortages, watersiders and other workers worked long hours, often as much as 15 hour days. Following the war, wages fell far behind the cost of living, and working hours continued to be high.

The waterside employers, the Waterfront Industry Commission , failed to abide by an Arbitration Court general wage order, saying the watersiders could live off overtime. The watersiders then refused to work overtime, and the employers locked them out.

The watersiders’ union had strong leadership. President Jock Barnes and secretary Toby Hill spearheaded trade unionism in New Zealand. The government and employers hated them because of it. The employers, through the newspapers which they owned, carried out long campaigns against the watersiders trying to isolate them from other workers. The employers were determined to smash the watersiders’ union and set out to provoke a dispute which they thought they could win.

The strike was a major political issue of the time. The government, led by Sidney Holland of the National Party, introduced Emergency Regulations, and brought in the army to work the wharves. Holland condemned the action as "industrial anarchy", and explicitly sought a mandate to deal with the strike in the 1951 elections. The government was re-elected with an increased majority. The opposition Labour Party, led by Walter Nash, attempted to take a moderate position in the dispute, with Nash saying that "we are not for the waterside workers, and we are not against them". Labour's neutral position merely ended up displeasing both sides, however, and Nash was widely accused of indecision and lack of courage.