Largest

The world's tallest wheel, the Singapore Flyer, is described as an observation wheel by its operators.

The London Eye  is also described as an observation wheel by its operators.

The Star of Nanchang  is usually referred to as a Ferris wheel, and less commonly as an observation wheel.

The Southern Star is described by its operators as "the only observation wheel in the southern hemisphere" but also as a Ferris wheel by the media.