The China Meteorological Administration said typhoon Talim, the fourth typhoon of the year, made landfall on the coast of Guangdong province at around 10:20 pm (1420 GMT), bearing maximum winds of 136.8 kilometers (85 miles) per hour, AFP reported.
Storm surges and lashing rains also hammered the southern coastline from Guangdong to Hainan provinces on Monday night, it said.
The forecaster had issued an orange alert, the second-highest warning in a four-tier color-coded system.
Nearly 230,000 people in Guangdong were evacuated to safety before the storm's landfall, including more than 8,000 fish-farm workers who were brought ashore, according to state news agency Xinhua.
The meteorological administration said the storm was moving to the northwest at a speed of about 20 kilometers per hour and could rake across the Guangxi region early Tuesday. Talim could lose speed by Tuesday morning and "weaken and dissipate over northern Vietnam" on Wednesday, it said.
Authorities in Vietnam said they were preparing to evacuate about 30,000 people from the areas forecast to be hardest hit in Quang Ninh and Hai Phong provinces from Monday afternoon.
Talim "might be one of the biggest to hit the Gulf of Tonkin in recent years", Vietnam's top disaster response committee said in an online statement.
Tourists have been advised to leave outlying islands and airlines have rescheduled services to avoid the storm.
AMK/PR