1846–47 United States House of Representatives elections

The 1846–47 United States House of Representatives elections were held on various dates in various states between August 2, 1846, and November 2, 1847. Each state set its own date for its elections to the House of Representatives. 228 elected members representing 29 states took their seats when the first session of the 30th United States Congress convened December 6, 1847. The new states of Iowa and Texas elected their first representatives during this election cycle. These elections were held during President James K. Polk's term.

The Whigs gained 37 seats to win 116 and a change in partisan control, while the rival Democrats lost 30, falling to 112. The Whigs gained seats in the Mid-Atlantic and the South. The nativist and anti-Catholic Native American Party, also known as the Know Nothings, was reduced to one seat. One Independent, Amos Tuck, was elected from New Hampshire.

The Mexican–American War, which the incumbent House had voted overwhelmingly to approve, was the main issue. The war had much stronger voter support in the West, South, and among Democrats than in the East, North, and among Whigs.

It was widely, accurately believed that war with Mexico would be won with large territorial gains. The Wilmot Proviso was the first congressional attempt to address slavery in these projected new territories, by proposing to ban it. Congress rejected the Wilmot Proviso, but not quickly or smoothly. Protracted debate aggravated sectional tensions. The repeated failure of Congress, and later also the President and Supreme Court, over the next decade to resolve the issue of slavery in the territories was a major cause of the Civil War.

This was the last time the Whig Party won a House majority, though candidates opposed to the Democratic Party would win a large majority in the realigning 1854 election. Notable freshmen included Abraham Lincoln of Illinois, elected as a Whig to his only term.