Elizabeth MacDonough is the current Parliamentarian of the United States Senate. She is the first female to hold the position.[1][2]
The Parliamentarian of the United States Senate is the official advisor to the United States Senate on the interpretation of Standing Rules of the United States Senate and parliamentary procedure.
As the Presiding Officer of the Senate may not be fully aware of the parliamentary situation currently facing the Senate, staff from the Senate Parliamentarian's office sit on the Senate dais to advise the Presiding Officer on how to respond to inquiries and motions from Senators. The role of the parliamentary staff is strictly advisory; the Presiding Officer is in no way required to follow their advice, though they almost always do so. The office also refers bills to the appropriate committees on behalf of the Senate's Presiding Officer. If facing the dais, the Parliamentarian is the second from the left.