The 1st Parliament of Ontario was in session from September 3, 1867, until February 25, 1871, just prior to the 1871 general election. This was the first session of the Legislature after Confederation succeeding the Legislative Assembly of the Province of Canada (last session was the 8th Parliament of the Province of Canada).

The 1867 general election produced a virtual tie between the Conservative Party led by John Sandfield Macdonald and the Liberal Party led informally by Archibald McKellar. Macdonald ended up securing the Premiership by leading a coalition government with the support of moderate Liberals. His Cabinet, nicknamed the Patent Combination, included two conservatives (John Carling and Matthew Crooks Cameron), a coalition Grit (Edmund Burke Wood) and two old school Baldwinite Reformers (Sandfield Macdonald himself and Stephen Richards). The first ministry would survive the first parliament by less than a year, resigning in December 1871.

In the first several years of Confederation, individuals could be elected to both federal and provincial parliaments and serve as MPs and MPPs at the same time. In the first Parliament of Ontario, provincial cabinet ministers John Sandfield Macdonald, Edmund Burke Wood, and John Carling all sat in both parliaments, as did Edward Blake, Thomas Roberts Ferguson, John Lorn McDougall (after 1869) and Frederick William Cumberland (after 1871). Generally, they represented the same riding, but it was not necessarily so; for example, Edward Blake represented Bruce South in the provincial parliament but Durham West at the federal level.

John Stevenson served as speaker for the assembly.^[1]

Below is a list of members of Ontario's first parliament. Bolded names are cabinet ministers; Capitalized names also sat in federal parliament.

• All Members serving in Parliament 1 Archived 2012-09-26 at the Wayback Machine