31 Building

{{Infobox building

| name = 31 Building

| native_name = 삼일빌딩

| native_name_lang = ko

| image = 31 Building (2013).jpg

| image_size =

| image_caption = 31 Building in 2013

| coordinates = {{coord|37|34|06.96|N|126|59|13.92|E|region:KR|display=inline,title}}

| address = 85, Cheonggyecheon-ro, Jongno-gu, Seoul, South Korea

| completion_date = {{start date and age|1970|}}

| renovation_date = {{start date and age|2020|}}

| building_type = Office

| architectural_style = International Style

| roof = {{convert|110|m|ft|abbr=on}}

| floor_count = 31 (equivalent)

| architect = Kim Chung-up

| designations = {{Designation list

|embed=yes

|designation1=Seoul Future Heritage

|designation1_number=2013-003

}}

| references = {{Cite web |url=https://www.emporis.com/buildings/106758 |archive-url=https://web.archive.org/web/20160306025759/https://www.emporis.com/buildings/106758 |url-status=usurped |archive-date=March 6, 2016 |title=Emporis building ID 106758 |work=Emporis}}{{skyscraperpage|12392}}{{Cite web |title=31빌딩(구 삼일로빌딩) |website=Seoul Future Heritage |publisher=Seoul Metropolitan Government |lang=ko |access-date=2025-03-30 |url=https://futureheritage.seoul.go.kr/futureHeritageMeet/futureHeritage/view.do?order=&htNo=342&htCateValue=&htSelectGuValue=&htConditionValue=&selectYearValue=&buildYearValue=&fetchStart=1&srchType=title&searchTitle=31}}

}}

31 Building ({{Korean|hangul=31빌딩}}), also called Samil Building, is an office building in Seoul, South Korea. Completed in 1970, the 31 Building was the tallest building in Seoul until 1979, when Lotte Hotel Seoul was completed.

The architect of the 31 Building was Kim Chung-up, a famous architect in South Korea.

It was selected as 'Seoul Future Heritage' because it is considered a valuable building in the history of architecture in Seoul.