www.umc.com

Exhibit

Exhibit Description

99.1 Announcement on 2026/02/13: Announcement of the Company's Board Meeting Date of 2025 Financial Reports

99.2 Announcement on 2026/02/09: the trading and pledge of UMC common shares by directors, executive officers and 10% shareholders of UMC

Announcement of the Company's Board Meeting Date of 2025 Financial Reports

1. Date of a notice of the board of directors meeting is issued: 2026/02/13

2. Expected date of the board of directors meeting is convened: 2026/02/25

3. Expected year and quarter of the financial reports or the annual self-assessed financial information submitted to the board of directors or approved by the board of directors: 2025 Financial Reports

4. Any other matters that need to be specified: None

.2

United Microelectronics Corporation

For the month of January, 2026

This is to report 1) the trading of directors, executive officers and 10% shareholders of United Microelectronics Corporation (“UMC”) (NYSE: UMC); 2) the pledge and clear of pledge of UMC common shares by directors, executive officers and 10% shareholders of UMC;