Does a severe speech delay always indicate autism?

Speech defects: No. There may be other neurological conditions involved.See a neurologist for further evaluation.

Speech delay: Severe speech delays do not mean autism.

Definitely not: There are plenty of reasons why a child might have speech delay. Autism is only 1 of them. Has the hearing been checked? Are there other delays in motor or social realms? Likely your child would benefit from a speech and language evaluation at a speech center specialized in children and potentially an ENT evaluation and other workup eg. Developmental evaluation if other delays are present.

No: There are many causes of delayed language development, the most common include hearing deficit, birth order (lower in the birth order, later talking), If other developmental milestones such as social and motor milestones are reached at expected times, autism is not likely. Speak to your pediatrician about your concern.