Commonly known as Webster's Third or W3 was published in September 1961. It was edited by Philip Babcock Gove and a team of lexicographers who spent 757 editor-years and $3.5 million. It contains more than 450,000 entries, including more than 100,000 new entries of the time. The Merriam-Webster staff has been working on the fourth edition (W4) of the Unabridged since 2008, but a publication date has not yet been set. It is not likely that Merriam-Webster will ever publish a paper version of W4 due to its unprecedented length.

Webster's Third New International Dictionary is a landmark in lexicography, one that sets the standard for scholarship and excellence. Its unsurpassed quality and reliability reflects 150 years of accumulated scholarship and makes this the premier unabridged dictionary in America today.