Internationalist Socialist Workers' Party

{{Expand Spanish|topic=gov|fa=yes|date=March 2017|Partido Obrero Socialista Internacionalista}}

{{Infobox political party

| country = Spain

| name = Internationalist Socialist Workers' Party

| native_name = Partido Obrero Socialista Internacionalista

| colorcode = {{party color|Internationalist Socialist Workers' Party}}

| logo = File:LOGO POSI.jpg

| leader =

| headquarters =

| foundation = 1980

| dissolution =

| predecessor =

| merged =

| successor =

| ideology = Trotskyism
Marxism

| position = Far-left

| colours =

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| website = [http://cartas.posicuarta.org/ www.posicuarta.org]

}}

The Internationalist Socialist Workers' Party ({{langx|es|Partido Obrero Socialista Internacionalista}}, POSI) is a Spanish political party of trotskyist ideology founded in 1980.{{cite web|url=http://www.historiaelectoral.com/pei.html |title=Partidos de extrema izquierda |language=es |publisher=historiaelectoral.com |access-date=29 March 2017}} It was a member of the Fourth International (ICR).