According to my Catholic church, it is a Holy Day of Obligation:
Ash Wednesday is a holy day of obligation. The Catechism of the Catholic Church states,The precept of the Church specifies the law [i.e. to keep the Lords Day holy]..... more precisely: On Sundays and other holy days of obligation the faithful are bound to participate in the Mass. "The precept of participating in the Mass is satisfied by assistance at a Mass, which is celebrated anywhere in a Catholic Rite either on the holy day or on the evening of the preceding day."[2180] In other words, it is sinful not to attend. If there is no serious reason preventing you from attending (e.g., illness, the care of infants), you need to go to Mass.