No. Many modern fixed-lens digital cameras are mirrorless, but fixed-lens cameras are not automatically mirrorless.

There have been fixed-lens cameras that use reflex viewing systems. Examples mentioned include:

• Olympus E-10: a fixed-lens digital camera with an SLR-style viewing system.
• Twin-lens reflex (TLR) cameras such as Rolleiflex/Yashica types: these have fixed lenses and use a mirror for the viewing lens.

In general, a mirror is only needed if the camera uses a reflex optical viewfinder system. If a fixed-lens camera uses an electronic viewfinder, direct optical finder, or rangefinder-style finder, it can be considered mirrorless. That’s why cameras like the Leica Q, Sony RX1, and Fujifilm X100 series are typically discussed without much emphasis on the “mirrorless” label: with fixed-lens cameras, the more important distinction is usually the viewfinder design rather than lens interchangeability.