| Election Name: | 2021 Tehran by-election |
| Country: | Iran |
| Type: | By-election |
| Election Date: | 18 June 2021 |
| Seats For Election: | The vacant seat for Tehran, Rey, Shemiranat, Eslamshahr and Pardis Triggered by death of Fatemeh Rahbar |
| Previous Election: | Iranian legislative election, 2020 (Tehran, Rey, Shemiranat and Eslamshahr) |
| Previous Year: | 2020 |
| Candidate1: | Esmaeil Kousari |
| Party1: | FIRS |
| Popular Vote1: | 346,645 |
| Percentage1: | 19.44% |
| Colour1: | no |
| Candidate2: | Hamid Rasaei |
| Party2: | FIRS |
| Popular Vote2: | 261,810 |
| Percentage2: | 14.68% |
| Colour2: | no |
| Candidate3: | Alireza Mahjoub |
| Party3: | WH |
| Popular Vote3: | 98,823 |
| Percentage3: | 5.54% |
| Colour3: | no |
| MP | |
| Posttitle: | Subsequent MP |
| After Election: | Esmaeil Kousari |
| Next Election: | Iranian legislative election, 2024 (Tehran, Rey, Shemiranat and Eslamshahr) |
| Next Year: | 2024 |
A by-election for the Islamic Consultative Assembly's constituency Tehran, Rey, Shemiranat, Eslamshahr and Pardis was held on 18 June 2021, to fill the vacancy caused by death of Fatemeh Rahbar. The voters cast their ballots along with the 2021 Iranian presidential election, the election for the City Council of Tehran, as well as another by-election for the Assembly of Experts.
It was won by Esmaeil Kousari, a brigadier general in the Islamic Revolutionary Guard Corps who had recently resigned from his office, and was officially supported by the conservative alliance Coalition Council of Islamic Revolution Forces. Two former MPs for the constituency, conservative Hamid Rasaei and Alireza Mahjoub of the Worker House ended up in the second and third place respectively.
The by-election had a low turnout, and is thought to have had an unprecedented number of invalid votes.
The top ten candidates out of 202 who ran for the seat, were:
| Candidate | Party | Votes | % | ||
|---|---|---|---|---|---|
| 1 | Esmaeil Kousari | Front of Islamic Revolution Stability | 346,645 | 19.44 | |
| 2 | Hamid Rasaei | Front of Islamic Revolution Stability | 261,810 | 14.68 | |
| 3 | Alireza Mahjoub | Worker House | 98,823 | 5.54 | |
| 4 | Ali Karbasi | — | 20,856 | 1.16 | |
| 5 | Zahra Saeidi-Mobarakeh | Zeynab Society | 16,112 | 0.90 | |
| 6 | Amir Aghasi | — | 9,453 | 0.05 | |
| 7 | Alireza Yazdani | — | 6,514 | 0.03 | |
| 8 | Asghar Azoureh | — | 5,994 | 0.03 | |
| 9 | Mehdi Marashi | — | 5,789 | 0.03 | |
| 10 | Reza Vahedi | — | 5,472 | 0.03 | |
| Blank/Invalid votes | Not Declared | ||||
| Total Votes | 1,783,003 | 100 | |||
| Source: [1] | |||||