Oltre alla Settimana dei Musei, ricordiamo che i direttori dei musei e i poli regio- nali hanno la facoltà, per via della riforma di Bonisoli, di aggiungere altre 8 gior- nate ticktfree a propria discrezione e 6 in concomitanza con ogni prima domeni-ca del mese da ottobre a marzo. In più è previsto che, se i minorenni possono ac- cedere sempre gratuitamente, dai 18 ai 25 i ragazzi pagano un ticket agevolato di 2 euro.
This link contains a better translation of the info above:
https://www.wantedinrome.com/news/italy-to-introduce-free-museum-week-in-march.html
This applies to ALL State Museums and Archeological sites in Italy.
Culture Week (Settimana di Cultura) runs from March 5-10th.
In addition to Culture Week and free Sundays mentioned (Oct-March) each museum will also have 8 additional free days to use at their discretion. Those have been determined for Colosseum, Forum and Palatine this year; reference the Coopculture website. Websites for other State museums should be checked for their discretionary free days although it's possible not all of them have been scheduled yet.
Regular entry prices for all young people between ages 18 - 25 has been reduced to €2.