Sir Walter Long, 1st Baronet of Whaddon (c. 1603 – 15 November 1672) was an English politician.
The second son of Henry Long (1564–1612) and Rebecca Bailey, Long was educated at Lincoln's Inn. He had inherited no land at his father's death, but when his elder brother Henry died soon after, he inherited the extensive but heavily encumbered family estates.
On 26 December 1621 he married Mary Coxe (died 1631) and by 1623 his debts had increased alarmingly. With the assistance of his father-in-law he obtained a seat for Salisbury in the 1625 Parliament, possibly as a means to avoid his creditors. He was elected to Parliament in 1626 as Knight of the Shire for Wiltshire.
Long was a vocal supporter of the remonstrance defending the House of Commons against the charge of unparliamentary proceedings, and played an active part in supporting Pembroke's attack on the Duke of Buckingham. In several speeches he questioned the duke's Protestantism and implied that the duke was involved in precipitating the death of James I.
In an attempt to prevent Long's return to Parliament in 1628, the crown picked him as High Sheriff of Wiltshire, but nevertheless he managed to secure a seat for Bath in Somerset, arguing on tentative legal grounds that since the constituency lay outside his county, he was not breaking the law. His continuing opposition to Buckingham finally resulted in his prosecution in October 1628 in a Star Chamber suit, and it was argued that Long had not only acted unlawfully in securing his election but also neglected his duties as Sheriff of Wiltshire.
Hoping to avoid censure, Long quickly withdrew to Wiltshire but returned to Parliament for the 1629 session. In the tumultuous scenes on 2 March, he took a leading part when the Speaker, John Finch, was forcibly held down in his chair, preventing adjournment of the House. Together with six others, he was arrested for offences committed within the House and appeared before the King's Bench, while simultaneously facing ongoing Star Chamber proceedings concerning his shrievalty.