Yes, Afghanistan is completely landlocked. It has no coastline on any ocean, sea, or major lake.
Being landlocked increases dependence on neighbors for trade access (especially Pakistan's Karachi Port and Iran's Chabahar Port), complicates economic development, and makes the country vulnerable to border closures and transit disputes. Historically, its location made it a strategic buffer and trade conduit between the Indian subcontinent, Central Asia, the Middle East, and China.