Which is the largest continuous sand desert on Earth?

The largest continuous sand desert on Earth is the Rub' al Khali, also known as the Empty Quarter. It occupies about 650,000 square kilometres across Saudi Arabia, Oman, the United Arab Emirates, and Yemen, making it one of the planet’s most immense dune landscapes.

The Rub' al Khali is part of the larger Arabian Desert, which explains a frequent quiz mistake. The Arabian Desert is the broader geographic region; the Rub' al Khali is the enormous, largely uninterrupted sand desert within it. Its name means “the Empty Quarter,” reflecting the harsh conditions and sparse settlement.

The desert stretches roughly 1,000 kilometres from southwest to northeast and reaches about 500 kilometres across in places. Its dunes can rise around 250 metres, while the surface also includes gravel plains, salt flats, and deposits left by ancient lakes. The sand often appears orange or reddish because of feldspar.

The Sahara is larger overall, but much of it consists of rocky plateaus, gravel plains, and other terrain rather than continuous sand. The Gobi is also predominantly rocky and gravelly, so neither is the best answer to this precise question.