Diane Evelyn Caldwell (born 11 September 1988) is an Irish professional footballer who plays as a defender for FC Zürich Frauen and the Republic of Ireland national team.

She played in 15 games in her debut year including 14 starts, scoring once, the tying goal late in a 2–1 comeback win over Fordham.

[7] Instead, Caldwell played for Albany Alleycats in the Women's Premier Soccer League (WPSL) in 2011 before joining Icelandic Úrvalsdeild team Þór/KA to finish the 2011 campaign.

With the owner heavily investing in the club including bringing in national team players from Norway, Sweden, Iceland and Brazil, Caldwell faced heavy competition for her place in the squad during the 2015 season.

[12] Bell most notably took Caldwell from being a versatile utility player in midfield and at full-back, and told her to focus playing at centre-back.

[10] During the COVID-19 pandemic with Germany in a lockdown and the Bundesliga still suspended, Caldwell and her Sand teammates volunteered as farm labourers to pick asparagus and strawberries to cover for the migrant worker shortage.

[15] On 19 January 2021, Caldwell returned to the United States to join North Carolina Courage of the National Women's Soccer League, signing a one-year contract with an additional option year.

[17] On 27 January 2022, Caldwell signed a short-term contract with Women's Super League club Manchester United for the remainder of the 2021–22 season.

[21] On 15 March 2006, Caldwell made her senior Republic of Ireland debut at the age of 17, appearing in a 4–0 defeat to Denmark in the 2006 Algarve Cup.

[24] Caldwell scored her first senior international goal on 6 March 2013 in a 5–1 win over Northern Ireland in the 2013 Cyprus Women's Cup, her 21st cap and her first playing in the number seven shirt following the retirement of Ciara Grant the previous month.