Portugal is consistently ranked among Europe's safest countries. Violent crime affecting tourists is very rare. The main concerns are pickpocketing in Lisbon's trams (particularly the famous Tram 28 through Alfama) and tourist-dense areas. Simple awareness and keeping bags in front is sufficient.
Beach safety requires some attention: the Atlantic coast has strong currents and waves that can be dangerous even for experienced swimmers. Always swim at supervised beaches (green flag) and pay attention to red and yellow flag conditions.