Aspect ratio locking alignment guides for gestures are disclosed. In one embodiment, a gesture is detected to resize a user interface element, and in response, a first alignment guide is visibly displayed, wherein the first alignment guide includes positions representing different sizes the user interface element can be resized to while maintaining the initial aspect ratio of the user interface element. While the user interface element is resized in accordance with the user gesture, and while the first alignment guide is visibly displayed: when the user gesture is substantially aligned with the first alignment guide, visible display of the first alignment guide is maintained; and when the user gesture substantially deviates from the first alignment guide, visible display of the first alignment guide is terminated.