Dutch poet and critic who was the driving intellectual force of the 1880 Dutch literary revival and the cofounder and mainstay of its periodical, De nieuwe gids (“The New Guide”). A ruthless critic of the rhetorical, passionless nature of traditional Dutch writing, Kloos continually championed the idea of beauty as the highest value in art and life.

In 1882 he published the poetry of his friend Jacques Perk, who had died prematurely. Kloos's inspired introduction, containing the maxim “poetry alone makes life worth living,” is regarded as the manifesto of the 1880 movement.

An admirer of the English Romantic poets John Keats and Percy Bysshe Shelley, Kloos determined to reestablish the sonnet as a valid art form with a new rhythmic freedom. His own early sonnets, collected in Verzen (1894), show his mastery of the form. Inspired by Herman Gorter's poem “Mei” (1889), the masterpiece of the movement, Kloos evolved the dictum that poetry should be “the most individual expression of the most individual emotion.” This aspect of the 1880 movement eventually proved the spiritual downfall of Kloos, for, unlike his fellow poets Gorter and Albert Verwey, he did not develop beyond this stage. His later poetic and critical works reflect the unbalanced, self-pitying, and self-adulatory condition into which he lapsed.