The 2005 floor crossing window period in South Africa was a period of 15 days, from 1 to 15 September 2005, in which members of the National Assembly and the provincial legislatures were able to cross the floor from one political party to another without giving up their seats.
Other existing parties mainly lost seats, with several entirely new parties being created; still-existing parties created in 2005 include the National Democratic Convention Seven of the nine provincial legislatures were also affected, with only the Free State and North West legislatures remaining unchanged.
In both the KwaZulu-Natal Provincial Legislature and the Western Cape Provincial Parliament the ANC received enough members to move from a plurality to an absolute majority; in KwaZulu-Natal it gained two members to control 40 of the 80 seats, while in the Western Cape it gained five, to give it 24 of the 42 seats.
This window period also saw the final demise of the New National Party, in which all its members crossed the floor, mostly to become ANC representatives.
The National Council of Provinces was reconstituted as a result of the changes in the provincial legislatures.