Three Chinese ships, including the Shandong aircraft carrier, passed through the Taiwan Strait on Saturday, the island's Ministry of National Defence said.
China claims self-ruled democratic Taiwan as its territory and has vowed to take it one day — by force if necessary.
Since Taiwanese President Tsai Ing-wen — who rejects that the island is part of China — was elected in 2016, Beijing has ramped up air and sea incursions around the island.
While the presence of Chinese warships is constantly monitored and announced near-daily by Taipei, the passage of the Shandong through the 180-kilometre- (110-mile-) wide Taiwan Strait is unusual.
"A (People's Liberation Army Navy) flotilla of 3 ships, led by the Shangdong aircraft carrier, passed through the Taiwan Strait around noon today," the ministry said in a statement, referring to China's navy.
The flotilla went "to the west of the median line, heading northward", it added, referring to the unofficial border in the middle of the strait which separates the island from continental Asia.
Saturday's latest show of force from Beijing comes more than a month after China launched aerial and naval exercises around the island.
The April war games saw Beijing simulate targeted strikes on Taiwan and encirclement of the island, including "sealing" it off, and state media reported dozens of planes had practised an "aerial blockade".
The Shandong also participated in those exercises, with J15 fighter jets deployed from it -- though the vessel was not in the Strait, southeast of Taiwan.
The war games were a response to Tsai's meeting with US House Speaker Kevin McCarthy in early April, an encounter Beijing had warned would provoke strong countermeasures.
Taiwan's armed forces said Saturday they "have monitored the situation and tasked (civil air patrol) aircraft, navy vessels, and land-based missile systems to respond to these activities".
In recent days, the island has seen an increased presence of Chinese ships and warplane incursions.
The defence ministry said 33 warplanes and 10 vessels were detected in the 24 hours to 6:00 am Saturday.
The day before, 11 vessels were near Taiwan's waters.
The last time officials confirmed the Shandong sailed through the Taiwan Strait was in March 2022, right before China's Xi Jinping and US President Joe Biden held a phone call.
Before that, the carrier transited in December 2020, a day after a US warship had passed through. The Shandong also made a sail-by in December 2019, weeks before Taiwanese voters went to the polls.